Someone told me that you will not find any fat old people. The implication was that fat people died young, but this isn't true. They just get skinny as they get older because they can't absorb nutrition like they did when they were younger. This is why they sell Ensure.
Another myth has to do with smokers. They do shorten their lives, but their average life expectancies are about six years less than the average. Some studies have them at the high range of 14 years while it drops to four if smokers quit at age 50. Most people think smokers drop dead at age 50, but this isn't true. Many of them make it to 70 but not much beyond that. The reality is that a smoker living today will dramatically outlive a nonsmoker from a century ago.
I don't have any stats on lifelong runners, but I think their stats will not be much better than the average. Just as smokers are seen to die 20+ years prematurely, runners are seen to be certain to live past 100. I don't see it that way. Old guys like Sheehan and Lebow never made it that long. Cancer got them.
I think people should stress quality over quantity in this regard. Living healthy feels better than living lousy. Having energy and breathing fresh air and being able to walk up a flight of stairs without getting winded are valuable things. Being able to play with your kids or go on a hike or surf in your 70's are quality things.
Longevity is in the hands of the doctors. Sorry. But the quality of your life is all up to you.