Wow, I did a metric century ride this past summer.  It was a lot of fun.  But, we didn't ride hard and stopped every 10-12 miles.  I would like to do an actual century this year but I'll have to continue to lose weight and bike, bike, bike.  The furthest I had ridden before the ride was around 26 miles continuously.  However, I made it with a little quad cramping on and off.