i did a bike'n'hike from fort collins to the top of longs peak a couple of years ago and started from my house at 8pm, just as it was getting dark, and got to big thompson canyon, the bulk of the climb, at about 9, and rode up the canyon in the quiet darkness.

other than creeping myself out thinking i heard bears, it was one of the best rides of my life and an experience i cant wait to do again sometime. maybe not the longs peak hike part but the canyon at night was amazing.