I like to think Elves go on an adventure at around age 70-90, get really super cool, take 100 years off, and then completely forget all their amazing skills because they've been learning the language of bees or doing sequoia trimming as a hobby for the last century.

Would be a cute fluffy class feature to just assign the very old elf an exceptionally difficult but totally useless skill at near-master level, to help explain why the Legendary Warrior of Old is now swinging for the minor leagues.