Hmm. Hard to say. How hard are you pushing it on these rides in terms of average speed (or if you keep track of it, heart rate)?

I ride 35 miles pretty much everyday, but I do it at a fairly leisurely pace (17-18 MPH) on flat ground. If I have a big climbing weekend ride planned, I take Friday off.

Then again, I DO fall asleep in front of the boob tube rather frequently.