I'm 56 and still running ultramarathons. I ran a 68.9 mile trail race in Croatia a month ago, and I'm running Western States 100 in June, then UTMB 171K in August. October will be the Marine Corps marathon to wind down the year.
It's noticeable in Europe especially, I see a lot of older folks in their late 50's and into their 60's doing these events. I'll be the first to admit that running races that long probably isn't the best for the body, and I'm quitting them after this year. But it is vitally important to keep moving, I saw the famous motion is lotion already stated above, it's true.
This is noticeable to me everyday as my job is mostly riding a desk, I make a point to get up at least every hour to move around, and twice a day I go out and walk around the building. I generally work out on my lunch break, I do not go out to eat. Even after a 100 mile race that takes more than 24 hours on your feet, it helps the next day to move around and walk to get the blood flowing through those tired muscles. Active recovery is so much better than resting too long.
My family has the genetics to live into the early 90's or so, provided we don't smoke cigarettes or abuse alcohol etc. I want to be like my wife's aunt. She is 92, and it seems like she is always doing something. She does taxes for other retired seniors and some of the 65 year olds look far worse than her. She also pounds the pavement going door to door soliciting people's votes come election time.
Bottom line, keep moving.