In Iain M Banks’ Culture novels people get several hundred years old. Death is pretty much optional, they just usually choose to die at some point. The way they deal with the problem of memory seems to be that they just take longer to do things; working somewhere for 30 years is a stint. You might follow a hobby for 20 years, or take a 10 year vacation.

But there was one character who chose to not die. He was over a thousand years old and an important witness to something that happened during the Idiran wars (iirc). He did have that problem, and he had outsourced large parts of his memeories. Electronically, and in the form of an explorable virtual world.

edit: I’m now not 100% sure about the 2nd paragraph. Maybe it was in a Culture novel, but differently, maybe somewhere else, maybe I’m mixing up two stories…