I'm surprised, it sounds like some of you go a long time on the bike without eating. I haven't ridden a century (yet), just a half and a metric. However I tend to go by time, not distance, as far as eating and drinking. (10 miles of climbing at elevation is NOT the same as 10 miles of gentle downhill in town). I recently attended a short talk by a rep from cliff bar who was also a certified sports nutritionist (and she stated very clearly that she didn't care whether the cliff products worked for us or not, but to find something that works). Even before this talk, this is similar to what I would shoot for and find it works for me, but was reinforced by this talk. So the basics are, eat a decent carby meal with a little protein preferably 1-2 hours before the ride. For me this is a bagel with cream cheese, OJ, and coffee. I will sip water up until I start the ride. Then, starting at about 45 min to an hour, consume 30 g of carbs and at least one water bottle per hour (more water if its hot). This can be either snacks (fig newtons, sports bars, blocks, gels), or in the form of sports drink with electrolytes if you can't stomach any food. (I love blocks, they are my snack of choice, but I mix those up with fig newtons and sports drinks for some variety). Then immediately post ride you want a recovery drink and/or food with a nice 4:1 carb: protien ratio. Try to eat a healthy meal within 30 mintues to 2 hours post ride. Don't skimp on the carbs, you need them to replenish your glycogen stores. Also, the day before I drink a ton of water, eat a healthy dinner, and no alcohol.

I'm not an expert, and everyone is different, but like I said this approach works well for me. I really make an effort to start eating blocks after 45 min of at least medium intensity riding, otherwise I will start getting tired and have a hard time getting my energy back. No way could I go 90 minutes without anything and keep going. My morning commute is 80 minutes, I don't eat on the way, but I don't have to ride any further. As soon as I get to work (I am STARVING by this point) I have a breakfast bar and a vitamin water, followed by some oatmeal, yogurt, and coffee post shower.