The Klamath Native American tribe has legends of the eruption of Mt. Mazama that formed Oregon's Crater Lake - which happened in ~5677 BC [1]. If oral legends that reflect real events can last seven and a half thousand years, is there any reason to think they couldn't last 15ky, or 20ky? It seems to me all that's needed is a continuous cultural line.

[1] https://en.wikipedia.org/wiki/Llao