Well, I think you have the ability to store up to 200 PMs, although I could wrong due to the fact I'm former staff and may have a larger inbox. If you're hitting the limit often, remember you have both Inbox and a "Sent Items" Mailbox. There is a Bar at the bottom on the page showing how full your inbox is.
Also, The PM inbox full alerts may not be possible due to the way vBulletin works. Serebii isn't the person to add to many Plug-ins to the forums.
As for Premium Membership? I don't think Serebii would be inclined to do this.
yea the thing is I like to keep my pms for records of trades and some kind of option for those of us who want it would be nice. it is nice though that it e-mails you when you are full, it just seems to be a bit late as it doesn't email you until you've already missed out on a PM so if a plug in isn't an option maybe they could change the setting where it e-mails you once you are full rather than after you have already missed one (or in my case several) PM's.
I do realize that there is a sent section as well. I'm constantly deleting posts from both sections.
If premium membership turned out to be popular then maybe serebii could upgrade the servers which was actually my next suggestion
I don't see how premium membership would really hurt anything, I don't recall running into limited inbox storage on other forums before and it can be really frustrating so some kind of option would be really great.
I think the layout is really great though and overall serebii.net is a great resource so I really appreciate everything that is here, just some kind of option for a MUCH bigger inbox would be great.
I do a lot of trading and there is usually about 10 messages per trade, and I probably would reach limit every two weeks or even less if I was doing a full purge every time but I have to keep some in storage to see what we have previously discussed so I'm purging less but much more frequently.
Seems like such a small limit is kind of discouraging to being more active on the forums which doesn't seem all that great to be honest. There needs to be some kind of option for a bigger inbox.