Actually a really good point I didn't think of. I believe it's something like 7 years for all our cells to be replaced. I suppose some form of cellular therapy could be used to extend our lives as well.
I think I get what you mean. It's sort of this idea of quantum immortality, I think? And also the concept of ideas and names outliving the person themselves. Although I think ideas and names would die off once there's no one left to remember or record them. Someone like Julius Caesar continues to live on in name despite being dead for thousands of years, but if humanity nukes itself into the stone age and we forget our own history, he'd cease to exist, no one would remember him.
I find quantum immortality really interesting to think about but quantum mechanics stuff overall goes a bit over my head so I don't have a ton to add. Plus I feel like everything I read about quantum immortality has a different interpretation of what it actually means.