It depends a lot on positions for me. If I'm tightened up things start going south in about an hour. I try to get on the tops on climbs (even shorter climbs, anything less than about 16 mph -- basically any time where I just don't care about being aero at all because I'm powering through it and wind is less of a factor), the drops when descending, and the hoods for like the other 60-70%...as long as I can do that I'm good for a while. My old shoes, no matter what I would have to loosen them after about an hour though, but since I changed from 44's to 44E's, I haven't had any discomfort in my feet.