Advice I've read says about 60 grams CHO/hour, or 240 calories. That seems plenty for me. I don't mess around with gels for long rides, prefer sport drink and rest stop breads or starch to the straight sugar. The gel sugar hit is good for a quick boost near the finish of a race, but I don't tolerate sugar very well during a long event. Four gel packs/hour wouldn't work for me.
We're all different of course. For me, the key is a good breakfast meal of pancakes or oatmeal with an egg, 1-2hours before the start. Some eating during the event is good, but it's easy to overdue it, in my experience.
I'm planning to do an unsupported Century tomorrow with some riding buddies. Will go with the good breakfast, a bottle of Cytomax, and a water bottle. My favorite food at convenience stops is the little peanut butter or cheese cracker sandwich packs...carbs plus some fat, protein and salt. About 240 calories each. Will probably eat 4 of those throughout the day, as well as another liter of Gatorade and a couple more liters of water.