I went from doing daily commutes to doing a 600 mile one-day ride from SC to Missouri, and had no problem, OTHER THAN sore butt, ringing ears, and numb shoulders! The bike on the other hand took it all in stride and would have easily gone another 600. Didn't realize it was that far from Denver to Yellowstone, but those states out there are bigger than they look on a map, so I'll have to keep that in mind when I plan a family trip from Denver to Yellowstone with KIDS!