Yeah, experimentation is key. Err on the safe side (bring extra food, even if you don't eat it) until you know what your body likes.

I'd likely pass out if I rode for 2 or 3 hrs without sugar. Trek has seen me in a hypoglycemic mess a few times, and those were just doing normal activity. (I think I might've been scary...) I bring *lots* of food even on little bike rides.