I have been thinking about for a while a solution to the idea that elves can live for hundreds, if not thousands of years and yet they do not seem to accrue any more skills or abilities or knowledge or wisdom than someone who doesn't live even 1/10th that length of time.
Working with the fact that elves don't have to sleep in D&D either, something that should just give them all that much more time to actually learn and improve. And yet... they just don't.
And it can't be that they are just unbearably dense, thick or stupid-- after all, when a player is playing one they advance at the exact same speed as any other race-- and, moreover, as of 4th edition WotC retconned in the idea that elves grow up just as fast as humans.
Now, I suppose there is the possibility that they could just out and out forget how to do everything after a short amount of downtime, but I am not even sure that works.
With most other solutions off the table, the only one I could come up with to explain this property is that although the body may live on, perhaps the identity of the individual does not. Perhaps every several years elves go into some sort of "hibernation" and in that time, perhaps all facets of their identity and memory and experiences gets lost. Or, if not lost, perhaps it gets shared to some sort of nebulous communal memory that they can all access while asleep.
When that elf then wakes up, they can have a completely different personality, have no recollection of their past and may not even choose to carry the same name. For all purposes they become an entirely new "person" who can have experiences and develop basically from scratch.
Although I hadn't considered the idea that they bodies might greatly morph as well as their minds, I think the idea that they could even switch sexes could work along with this idea.