Organized century rides can be fun/social events if you approach them with the right attitude. Some folks view them as a race and while that can be satisfying, you can do that on your own anytime. I prefer to go out with an open mind and see what develops. Sometimes you run into a group of riders that are just fun to be with and you don't care about your finishing time. Sometimes you never seem to find the folks that want to ride at your pace and you ride almost the entire route alone. The most satisfying century ride I ever did I rode on my MTB as "sweep" and helped the very last rider on the course finish the ride by offering encouragement and a good draft. I made sure that she finished before me so that she was not the very last finisher.

The most fun I have ever had were on overnight rides where you ride out to some destination on Saturday and ride back on Sunday. My experience with such rides was on numerous TOSRV-South rides in the 1980's from Tallahassee, FL to Albany, GA and back. Very memorable rides and the sense of accomplishment after back-to-back century rides far surpasses what you get from a single century ride. I can only image how much fun RAGBRI (sp?) or the original TOSRV in Ohio must be.