Chromosomes have a limited number of telomeres, each time the cell divides the telomeres become shorter. If your cell runs out of telomeres it can't divide anymore. This is one of the primary mechanisms the body balances repair against cancer risk. Current max of human life is about 120. If you don't "solve" the telomere problem you are not going to extend life past 120, though you may have more people live that long and may improve quality of life in later years.
Our species has a good balance that lets us live well past reproduction age, presumably because there is evolutionary pressure (benefit) to having elderly people around to pass on knowledge, help raise grandchildren, etc.
You can do things that extend the telomeres, but that makes cells more likely to reproduce out of control (cancer). This is a very hard "problem" to solve because cell final death is so important in preventing cancer. We are not even close to solving this, it would require revolutionary biological understanding.
Nanobots at some point may be able to essentially destroy bad/old cells, and maybe feed/nourish good cells we want to keep, and when cells can't divide anymore, could those be replaced with ones that could ?
I think back to the movie Bicentennial man, where he made completely real working human / robot interchangeable parts that basically allow for increased life and better health. Sure it's a movie, but we can 3d print organs and things, so it's not outside the realm of possibility...
In a sci-fi hypothetical where nanobytes can do arbitrary behaviors, sure, maybe they could intelligently do that. But that's an extremely complex thing.
My point to my original post is really that if anyone hears a "longer life" breakthru that doesn't even mention telomeres, I immediately move on. If they moved the needle on well-being of the elderly a bit, that's great. But nobody's "solving aging" without telomeres.
This seems like part of the puzzle. First repair the damage, then extend the time span, and the more you do this the more opportunities you have to find an optimal solution.
I think the only thing that will actually work is for entirely new bodies to be built and for our minds to be copied over.
It's not immortality but that is probably as close as we will get, and once we can do that then extending our current body's lifespan will be exponentially easier.
Evolution doesn’t optimise for length of life, just propagation. A number of species have evolved to have very short life cycles because that enabled greater propagation. Presumably shorter lives generally confer greater adaptability as it increases the opportunity for evolutionary change