Everlasting
Everything stays.
Wiki:
"Because of their association with the ballet La Sylphide, where sylphs are identified with fairies and the medieval legends of fairyland, as well as a confusion with other "airy spirits" (e.g., in William Shakespeare's A Midsummer Night's Dream), a slender girl may be referred to as a sylph.
Sylph has passed into general language as a term for minor spirits, elementals, or faeries of the air. Fantasy authors will sometimes employ sylphs in their fiction. Sylphs could create giant artistic clouds in the skies with their airy wings."
And the German name says it flat out: Feelinara. Fee = fairy, literally.
Sylveon can be a fairy Pokémon without having a type named on it, just like Clefairy and Snubbull. Don't forget we don't know Sylveon's specie yet.