Do you have a number in mind? Do you want to live to be 80, 90 or 100? How about 115 or 120?
I would like to live to be at least 100 but I realize how difficult that will be to accomplish. There will be some obstacles to overcome.
Do you think it matters what your expectations are? I do. I think if you expect to live a long healthy life, your chances of doing so are greater.