You, I, and everyone we know have bodies that are incredibly unlikely to make it past 120. They're just not built to last.

That used to be the standard wisdom, but it is now disputed. There is evidence that aging stops. True, for humans it does so only when we are already decrepit and stand a substantial chance per year of dying, but some other animals stop aging before that point. So it is not beyond hope that we might make our bodies last much, much longer.

ETA: Googling further, I found Michael Rose's 55 theses.

At the heart of the challenge of the 55 theses is this idea – That most of our health is not dependent on the health institutions but on evolved biology. If we fit our lives closely to our evolutionary design, then we will age well.

And one of the things he writes about is the cessation of aging, of how earlier cessation can be bred for in experimental animals (don't let them breed after a certain age: the earlier they stop reproducing, the earlier their cessation of aging evolves to be), and of measures the individual can take to promote their personal cessation of aging.

I have only glanced through this enough to think it worth posting here.