But who decides when it’s time to stop?

Jon Mendes, a retired investment banker, will turn 94 the day after the marathon, and he will be the oldest man to finish the race if he’s able to walk the entire course. He told me that his children and grandchildren sat him down earlier this week and told him they were worried about his endeavor.

“They said: ‘We’re not happy about this. If you feel that something’s not right, you just have to leave,’ ” he said. “I told them: ‘If I feel any discomfort, I’m out of there. I’ll be fine.'”

Mendes walks at least two or three miles a day and has completed more than a dozen marathons. Last year, he covered about eight miles of the New York City Marathon before dropping out because he was just too exhausted. When I asked him why he would try the race again, he answered as if I had asked him why he bothered to get out of bed every morning.

“I’ve lived an outdoor life, starting with the Boy Scouts, then camping and skiing and going to Dartmouth up in the woods and being in the Marine Corps,” he said. “I’m seeing all of my doctors, and am reasonably qualified to try to run, so why not?”

Point taken.

Why shouldn’t Margaret Hagerty run her first New York City marathon at age 91? Hagerty has already run 80 other marathons, and she is already the oldest person to complete a marathon on each of the seven continents. Just last year, she competed in a half-marathon on Mount Kilimanjaro.