I've only owned Mountain Bikes but have done a good deal of road riding on it, breaking for the trails when I come across them in my travels.
The tops I've done was with my first ride, a Trek 930--a low-end performance ride, but quite a substantial upgrade from the old Huffy. I left at 9am and was back for lunch around 1pm after doing 62mi. I recall it was the rock hard racing seat that did me in, though, rubbing the 'sweet-spot' raw (I hadn't bought a pair of riding shorts yet). Might've been able to pull of more, but Mr. Wood Devil was gettin' hungry