I think a study of the heath of people who participated in Iron Man events, professional cyclists, etc, these types of folks would be interesting, especially to see what the long term effects of this, and particularly when they hit their retirement years.

I've heard that NFL players don't fare particularly well when it comes to living a long time, but that's a totally different type of activity, and no doubt the general lifestyle of an NFL player would be a factor.

I personally don't think there is a key to living a long life. My FIL lived as long as Jack Lalane, who was a health and fitness fanatic. What's amazing is that my FIL, was obese, did almost no exercise, did not eat healthy and smoked part of his life, yet he didn't have to see a DR. till he developed AFib at 90, and was mentally sharp till the day he died.