I'm on the South side of 68 and ride from 10-12 miles per (non-golfing) day on my mountain bike. For golfing days that means some 5 miles of hilly walking (there are still a handful of walkers at our club) and ball-striking.
I don't think it's bad for an old man who had bypass heart surgery in 1990. I renetly wore out my first (1992) bike (a $400 model) and believe it or not, found a decent replacement at Wal-mart for $139.
Here in South Arkansas my riding season is when the temperature is above 70 degrees F., from March through November. In March my biggest problem is getting used to a sore butt. Yes, I've tried different seats.
The following photo was published several weeks ago in TIME. Note what these Tour de France riders are doing prior to a large hill climb in order to strengthen their lungs.
Len Miller