....and I suspect that worrying about whether you're doing too much or not enough exercise takes another 2 yrs off of one's lifespan? I'm 67 and do 350 min walking, 30 min rowing, 90 min lifting per week. One can pretty much feel the benefits, better sleep, muscle mass maintenance, weight stabilization, less net inflammation, stronger immune system. The "too much" is the point of possible injury or when your mind says "no". One probably needs to give in to the inevitability of aging process also.