I think most people would prefer a scenario where they live to the age of 80 at the kind of physical peak they attained in their 20s to one where they live to 1

I think most people would prefer a scenario where they live to the age of 80 at the kind of physical peak they attained in their 20s to one where they live to 120 in a state of ever increasing decrepitude. Put another way, the dream is to give you 5 decades of being 25, not 5 decades of being 85.