Of all the ways I was imagining this Doctor might die, old age was the last thing I would have expected. But having seen it happen now, I think it probably was the most fitting way for him to go. We never knew until recently, but all along the Eleventh Doctor was on what was meant to be his last ever body, so all along he would have known that once he dies, that's the end, no matter what. In a couple of recent episodes there have been indications that the Doctor didn't want his end to be a violent one in the midst of battle, and that he sort of perhaps hoped one day he'd just kind of retire and be able to live out his final days peacefully. This is probably the only chance there ever has or ever will be to tell a story of the Doctor finding a place to settle down and grow old, albeit, this being the Doctor, without it being anywhere near as simple or peaceful as that.
So, kudos to Steven Moffat for managing to write a story that's about the Doctor regenerating of old age. The last two times the Doctor did that, it was just sort of an incidental thing that occurred at the end of a totally unrelated adventure because his body happened to be wearing a bit thin. But here, as soon as the Doctor had figured out what was going on with the crack and the Question and sent Clara home, it was as if in that moment he'd essentially chosen his fate of dying of old age on Trenzalore. (It's quite a thing to discover that this Doctor's worst fear in The God Complex was the crack because he'd always been afraid it would come back one more time and cause a situation as drastic and inescapable as this.) Interesting to note is that the Doctor could potentially have defused the conflict from the start by just killing himself there and then, since then the Time Lords would never have been able to get through and everyone could have gone home - and that's the same reason he should have let himself get killed at Lake Silencio like he was supposed to - but he didn't because he was still determined to hold onto some kind of life, even if not quite the life he usually led, for as long as possible.
If you'd gone back and told a past-me that the Eleventh Doctor would spend a large chunk of his final episode looking older and not like he usually does, I imagine I'd have been disappointed. But I'm actually not, now - he may have looked older and walked with a cane and a limp, but he still acted like the Doctor we know, so I still completely saw him as the Doctor. This Doctor's often been described as "an old man in a young man's body", so having his body finally reflect how old he is on the inside seemed appropriate and really worked, for me. I have to admit it did take me a little while to accept and get my head around the fact that the Doctor spent three hundred years of his life on Trenzalore, protecting Christmas - but it didn't feel like as big a leap as it could have been. Because, throughout this Doctor's run, I've become used to the idea that a century or two of his life might just be wasted away in the blink of an eye, and that despite the immensely long time he just lived through, he really doesn't change that much. The only thing that really changes him as a person is when his companions come and go. And, having sent Clara home, he spent all that time on Trenzalore without any proper companions; Clara and her safety were still his biggest priority during the times she came back, just like she always was.
In some ways it's really sweet and heartwarming that the Doctor was willing to give up his life of adventure and travelling - and being with Clara - just to protect one little town that needed him because he couldn't just turn his back and let it burn. It just goes to show how kind he is, sacrificing all that for people that at the time he didn't even know. At least those centuries can't have been anywhere near as sad and lonely for him as the ones he spent wasting time in between seeing his companions. Despite being stuck in one place, hopefully he didn't even get too bored, as it seems he passed the time in between invasions by telling everyone stories of all of his past adventures - not to mention being a terrible influence on generations of kids by teaching them his definition of "cool" and how to do the Drunk Giraffe. (I was so gleeful to see the return of his awful dance moves from The Big Bang, and even more so to hear it canonically named after the way Karen once described Matt. x3)
However, while he clearly grew to love the town and the community as a whole, I think he probably always tried not to get too attached to any one particular person, because humans age so much faster than him and he'd have had to bury so many loved ones in those three hundred years if he became too close. It's very telling that he got so upset when Handles shut down; despite it being an emotionless computer, it seems the Doctor grew attached to it because it was his one constant friend who wouldn't ever die on him (or so he thought). It also seems that, despite himself, he couldn't help but get a little more attached to one particular kid than all the others. I think his decision to return even after he had the chance to leave was swayed by the way Barnable absolutely believed he'd come back and said he'd wait for him - sound a bit similar to a certain other someone who always meant the world to this Doctor?
It would appear that the Doctor (well, this Doctor, at least) ages exponentially faster as the years go by. For the first three centuries that we knew him for, he barely visibly aged at all, but then after the next three centuries that he spent protecting Christmas, he looked about twenty human years older. So it's not too much to assume that aging from that point to the oldest we saw him at here didn't actually take that long, even though that'd be another forty or fifty years for a human. Which is good, because I can't believe that the actual battle part of the war on Trenzalore would have taken more than a handful of years for it to go from equal footing to Daleks almost completely obliterating everything else.
On Clara's end, the events of this episode must have been heartbreaking, having to watch her best friend, someone she thought would never grow old and die, do just that in the space of one Christmas afternoon. Usually that's the other way around in a Doctor-companion relationship. And the two times he sent her away were like punches to the gut, even though she must have known he was just keeping her safe, especially the second time after he'd looked her in the eye and promised he wouldn't (at which I knew he was lying straight away) and aaaagh. Good on her for being so determined to change his fate somehow. Her speech into the crack about how his name is the Doctor is exactly what I've felt about the issue of the Question for a while now. Damn right that it talked some sense into those silly Time Lords. They should have figured out long before then that coming through here in this way was just going to cause chaos and left much sooner. At least they had the decency to give the Doctor extra regenerations for his trouble, seeing as it was basically on their account that he was dying, before disappearing again.
I was glad that he happened to temporarily de-age so that, for his final farewell scene, we saw the Doctor as we'd always known him. He also evidently went to the trouble of changing back into his more usual outfit, as if he wanted to die "as himself", so to speak, rather than as Christmas's protector who wasn't quite the Doctor he'd always been. Fwee for him eating fish fingers and custard one last time, during his pre-regenerative stress that probably involved an awful lot of pain - further evidence towards my silly little theory that fish fingers and custard has always been like a painkiller for this Doctor! Then it was interesting to see his reaction to being confronted with imminent regeneration, considering that his entire life up until now that'd never been an option so he'd never really had to decide how he feels about it. It struck me as similar to how the Tenth Doctor had felt about it, except this Doctor wasn't quite so dramatic as to describe it as "death", but it's still such an instant, complete loss of the identity he's had for so long that he has every right to find it frightening.
And then the one thing, out of everything, that could have made me find this Doctor's regeneration scene as utterly heartwrenching as possible was for him to go and hallucinate Amelia - and then Amy - as he's about to go. There'd been times in the past when he'd deal with the fact that he was dying and afraid by pretending Amelia/Amy was there even though she really really wasn't (voice interface!). And he said, when he explained how Amelia was the first face he saw, that she always would be seared onto his hearts - this incarnation's hearts, that is - and she really still is, even now after he'd moved on and found Clara who's also incredibly important to him. So to have him reach out to his Amelia one last time, to be hallucinating and momentarily believing she's actually there with him even though he knows that's completely impossible... gah. D: And Amy's words to him were so close to the last words the real Amy ever said to him and d'aww. ;;
One of the last things he did was to take off his own bow tie! While obviously the next Doctor should not be seen wearing a bow tie, this way is all the more poignant than if the Twelfth had taken it off afterwards. This is like the Eleventh Doctor admitting and accepting that he is about to stop existing, which is really all kinds of heartbreaking. Then I actually quite like the way the change itself was really abrupt and surprising. I also have a personal interpretation for why it was so quick, which is that because Clara was reaching for his hand, he was so close that the regeneration energy risked hurting her once it got to the explodey part. So he sacrificed the chance to have a few more seconds as himself in favour of changing as quickly as possible so that it was over in a flash and she wouldn't be harmed. It's also just incredibly sweet that, after realising Amy wasn't really there, he reached out to Clara instead, possibly to try and reassure her, or possibly just because she's real and another source of comfort for him in his final moments.
Oh, Amy and Clara. To me, this Doctor's run has been so focused around these two impossible girls who've meant so much to him, so to have them both play a part in his farewell is exactly as it should be.
I guess it could be explained by her inability to kill them, so the instinct didn't kick in, but wouldn't she still recall seeing the Silent from the moon landing footage? Oh, and why did the Angel that grabbed her leg do absolutely nothing? A pointless addition, I'm afraid.