Weather and time. I live on a ridge in eastern CT and the wind takes a lot of the fun out of riding. We've also had some ungodly hot days and days of deluge. I'd ride with my club but they go out on a Saturday and/or Sunday and ride for 4-5 hours. I just don't want to devote that much time to cycling on a weekend. I end up doing 3 rides a week in the form of a 15 mi. TT, a slow 25 mi. ride with my gf and then third ride however I'm feeling at the time. Sometimes that's a hard 20 mi. ride and sometimes a "brisk" 35 mi. ride.