I sure the government would say 65.5 years, that way the get to keep all the SSI money. Personally I'd say around 80, which is much longer than males in my family live. The oldest male in my family made it to 72.
In years, what do you think would be the optimal life expentancy for humans? In other words, how long would you like human beings to live on average? This is a philosophical question. If humans had bodies designed to live much longer than they do now, the world and a human's life would be very different. Consider this in your answer.
For recent years in Swaziland life span is about 49 years (lowest) while in Japan is about 83 years (highest).
Right now? 60 years. That way you can avoid most degenerative issues and end life with most of your faculties still there. Hopefully we can push the body degeneration starting point further and further as technology progresses, but right now, on average, it's untenable.
A large number of human beings, when posed with this question, basically settle on something like 80, even when decrepitude is removed from the picture. It seems that we psychologically are generally attuned to want to live for roughly as long as we will anyways.
I personally would want a human life span to last as long as a person is still ready to live.