On Monday, my husband and I did this (our watches weren't up to the task so I'll do the math for you - it equals 101.38 miles).
This post is not about being braggy, because we don't look like the bikers pictured above. We are middle aged suburbanites who don't belong to a gym anymore. Our equipment isn't particularly expensive (other than recent upgrades to this helmet to protect our noggins). But we happen to live in a town with great bike trails, so one day, my husband said, "What if we did 100 miles in one day?" (He's great at ideas like this).
We picked a date a few months out, and our 100 mile goal became a good motivator to back away from the laptops and get outside for some exercise. But next thing we knew, the day was here. We were feeling pretty good at the halfway point:
We were feeling waaaay less good at about 75 miles:
But rallied to finish. Also we had no back up plan if we quit before getting home - ha!
So the shocking realization: goals are good motivators. But also, you don't have give up on outlandish physical goals just because you are north of 50 years old.