Live to 100? As someone who has known people to live until their mid-90s and still had sharp minds and good mobility, I have come to believe that quality of life is more important than age. If I could still be as mentally and physically agile as the ones I've known, then I would look forward to watching my grandkids grow.
But my attitude has always been I want to live as long as it's fun. Take all the pleasures I enjoy away from me and I would have nothing to look forward to during the day. If I can't read, smoke my pipe, have an occasional alcoholic beverage, find something to laugh about, then I'm not sure I would be "alive" anyway. Without those I would just be a biological mass existing without reason.