I'll be 66 in a couple of weeks and my fixed road bike is 49-17 which is 76 inches. I ride an 18.2 route selected for as few large hills as possible, at least 4 days a week. A normal time is about an hour and 15 minutes including warmup.

This gearing is pretty perfect for the route I ride and my strength and endurance. Can handle the hills both up and and down and decent speed on the flatter areas of my route.