Not speaking in exact years, until I lose my mental capacities. When I can't even be in control of my own thoughts, basic actions, and emotions, just off me then and there, that's no life I want to live. If I can keep my health and mental capacities, as well as youth and physicallity. Until I'm happy to die. Until I've seen the world, rode an elephant, gotten into a sword fight with my old elementary school bully, and climbed a mountain while simultaneously playing Pokemon Gold and making out with a super model.
Speaking in exact years, 64, 80 seems like a good place to go.