I have a comprehensive report on my great-great grandfather and his descendents, from where I got a lot of my information. The rest I got from other sources.
I don't expect to live forever and medical sciene has improved but not that much.
You are correct, none of us knows when our time is up BUT I'm 65 1/2 and I had a heart attack two years ago, followed by by-pass surgery. My cardiologist is not particularly optimistic about the tests I've been taking. Now how would you like to living in those circumstances. Wouldn't you suspect your time will be up pretty darn soon? I don't worry too much about it though since death does not scare me.
But all but one of those is still living.Your time is up when it's up. You could go somewhere today and get killed in a car wreck.