I really don't believe that who I feel I want to be has anything to do with what time I die.
Besides, how am I supposed to compare my lifespan? To other people? They aren't me. They don't have my body or my brain. So, really, it's pretty pointless. He lives to be 70, she lives to be 100, I die when I die. I know there's that fear of regrets on your deathbed (if you're lucky enough to get a deathbed), but I really doubt anyone wants to die, even if they think they do.
It's biologically contrary to our objectives to want to die. No one really wants that. Most people who want "death" just want a pain, either physical or emotional, to end and they believe death is ultimate painkiller. If someone gave them a guaranteed option to take the pain away without dying, they'd take that route. Or, at least, that's what I believe. I wouldn't honestly know; I'm not them, after all.
Besides, I could be the healthiest son-of-a-bitch in the whole damn city and still get hit by a bus, couldn't I?