The first time that I rode 100+ miles, I did it solo, and just for the heck of it to see whether I could. I was riding the route of a local club's group ride, that had a metric, a 42, and a 21 built into it from the same starting point. I had ridden the metric several times previously. I set out with plans to just do the metric. When I got back to the start point, I took a short snack break (like 3-5 minutes) and on the spur of the moment, feeling still pretty fresh, I took off again over the 42 mile route. It was in the spring, with longer days, pretty mild, not a lot of wind. No big deal. I was tired but nowhere near exhausted at the end of 104 miles.

For my next trick, two months later, it was 100 and 75 miles on consecutive days in a charity ride. I have to admit that I had to really tough it out the last 10 miles of day 2, riding uphill into the wind.