Yep, me too. But I think it's the flat terrain and repetitive movement that's to blame, not the speed (apart from it being boring in addition). I can bike 2-3 hrs every single day, or hike all day, but a day's Christmas shopping will kill me.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett