Re the calories, I have a Garmin 405 (I think that's the model?) that keeps track of speed, distance, heart rate and a bunch of other stuff I am too lazy to research so the 2500 calories @ 16.8 mph is taken from that. I live in Illinois, outside of Chicago, so it's pretty flat, although I live pretty close to the mighty DuPage River which puts about 500' of elevation change in the mix depending on where I go. Most of the interesting trails seem to run along the river so going down the hill to the trail and then back up to ride along to the next one is part of the deal. I have had a couple of times where I've ridden faster one day for the same distance I rode slower at the next day and burnt more calories the slower ride b/c of the longer duration. Which is a pleasant reward and sort of food for thought? Or thought for the food to eat to replace the calories? "If I ride slower, I can SuperSize it!" I usually ride as fast as I can. Longer distance is sort of dependant on energy level and plans and stuff.