Well, I'm definitely an early riser (before 6AM on most days), and I get some degree of exercise on most days (12 miles of cyclo-commute on office days, longer

Well, I'm definitely an early riser (before 6AM on most days), and I get some degree of exercise on most days (12 miles of cyclo-commute on office days, longer rides on other days), and I'm generally good 'til about 9:30PM. After that, I definitely start to crash. However...if I go to the climbing gym at, say, 6:30PM or 7PM, and stay for 90 minutes, I can make it a little further into the night without being tired.