Originally Posted by WhyFi

Unless you've got some kind of medical condition, I don't think that you should really *need* constant fueling at ~3hrs of low or even moderate intensity; your body should have a couple thousand calories on tap via glycogen stores. If you can, start doing your shorter rides in the morning while fasted, and at low-ish intensity (Zone 2) to get your body (and mind) used to the load, while working off of reserves. I can wake up and hammer out 62miles/100km with nothing but water (beyond that, my output starts to droop unless I have some snackies).

Oh, and pay attention to your water intake. I think that a lot of people that "bonk" on the bike are dehydrated, rather than running out of fuel.