My dad rode at least occasionally until he was in the late stages of prostate cancer at 83. He started cycling just before WWII because he couldn't afford a car, but found that he enjoyed it and, after the war, used to ride from our house on the east side of the San Francisco peninsula over to the ocean on the west side--only about 25 miles, but in those days, on a single-speed Raleigh, that was a long way. He quit for several years in his 40s and 50s, but picked it up again at about 60, after all his kids moved out. At about 75 he began to have inner ear problems that affected his balance, and he refused to wear a helmet until he took a pretty bad fall. Then he switched to an adult tricycle, but it was such a heavy and clumsy POS that he hated it. He was looking at one of those "feet-flat-on-the-floor" bikes (I forget what they're called--like the Electra Townie) when his cancer was diagnosed, but still rode the trike up until about six months before he died. He enjoyed the exercise, and since he'd pretty much quit driving, it gave him at least a feeling of freedom, if not really much actual freedom. I used to worry about safety, but by that point, he said, "The best thing that can happen is that I get hit by a car."