Of the three elves we’ve met so far (there might be one or two other minor ones in flashbacks) only Kraft can be said to have changed class (warrior to monk), and that was centuries before the time of the series at the earliest, and due to a crisis of faith (and possibly a midlife crisis, or the elven equivalent of one).
The other two have spent at least a thousand years focusing on very specific skillsets (and in Serie’s case complaining about how humans don’t live long enough to gain proper expertise at their crafts)…
The premise of the series is Frieren learning to appreciate her friends despite their short lives (well, the original premise was a cute immortal terrifying demon killing machine of an elf, according to the author, but it sort of evolved from that)… but when it comes to the nature of elves and how they learn, it’s pretty much the absolute opposite of this.
Both Frieren and Serie would be extremely offended at the mere suggestion that they might possibly ever forget anything, and Kraft would probably be disappointed but understanding.
What. She’s basically got photographic memory. The whole series is built on flashbacks to her memories.
She’s dense as fuck when it comes to interacting with people, sure (though she’s been getting better), possibly due to being an elf, possibly due to having spent most of her life alone in the woods, and she’s extremely disorganised, but she remembers perfectly every single word of conversations held a thousand years ago.
Remember the sour grapes, remember her conversation with Old Man Voll when she was offended at the suggestion of her possibly not remembering until she realised he really was senile, remember how she could tell that the steaks in the restaurant tasted different than they had over eighty years before.