I will be hitting 63 in a couple months. The first of July I got a new bike (replacing the Safari which died an honorable death on the back of my Camry, which got rear-ended), and I've been training fairly strenuously, progressively longer rides but not fast: touring speed. Gradually I worked up to 52 mile rides (with 1900+ feet elevation gain, some really nice hills) which at first were followed by a nap and then a rest day. Since Aug 1, I've been riding 52 mile rides two days in a row, with a rest day next, followed by 2 more days of 52 miles, until this weekend when I've ridden 3 - 52 mile loops each day, Fri Sat Sun (total 360+ miles in 7 days of pedaling over 9 calendar days). I'm kinda tired this afternoon but not really dead yet. Feels good. If it is bad for me, I don't care. Gonna rest tomorrow, then ride 2 days, rest, then ride maybe 3 or 4 days in a row, depending how I feel. The loop takes about 4 hrs pedaling, at about 13mph, and I stop now and then to drink, eat, etc. My plan is to gain endurance (more days in a row) and then take some side roads on my route to extend the distance. Last fall I rode the Natchez Trace (450 miles) in 9 days of pedaling over 12 calendar days, and I felt better at the end than I have in years.