What KSH said plus 1.

Try lowering your pace early on. If you're on a long ride, ride the first half easy, like you could go all day, then if you wnat to push you can kick it up a bit in the second half. This is called a negative split and it's a great way to increase aerobic endurance.

I would also try to eat something on your ride, beyond the energy drink. I like gels myself. My stomach can't handle anything to heavy while I ride. My favorites are Gu and Accelerade (sp). You take them every 45 min to 1 hour during activity. Then on the really long rides I'll stop at a store at the mid point and buy a coke and/or a chocolate bar. It really helps to maintain the glycogen in my quads on the 4 plus hour rides.