Who're you trying to impress? Slow down and enjoy the ride, then afterwards you can enjoy the afterglow. I'm 68 and ride pretty slow, but a 40 mile ride doesn't make me tired at all. My normal daily ride is 30+, and I try to do longer rides on the weekend. Two weeks ago, I rode 101 and wasn't particulary tired. LSD wins the day when you pass the big 50.