I don't see how it would improve life overall, except for duration. I see many areas where life would become worse because of it, so i am biased, true.
But your scenario implies that it is already a reality, which it is not, and that i would be in favor of killing people, which i am not. I am simply suggesting one thing: Maybe we shouldn't be able to live as long as we want, maybe we should not try to make this a reality.
I think we differ here because to me, if life is good, extending duration is enough; it doesn't need to be even better.
> But your scenario implies that it is already a reality, which it is not, and that i would be in favor of killing people, which i am not.
I apologize, I tried hard to avoid implying that. I am only saying that if we were in my preferred world, very few people would advocate to turn it into this one. They would try to improve the preferred world in other ways to fix the problems that exist there. By symmetry, I argue that it means at a minimum that turning our world into that one is an improvement. (Though there may be other, different, ways to improve it!)