I agree with all of the above that said (in one way or another) "It really varies with the ride!"
I've ridden centuries without stopping (fueled by Sustained Energy in a Camelback and two large bottles of Gatorade), and I've ridden as little as 6 mi. between stops (The Lake Pepin 3-Speed Tour) with eating opportunities (great pie in Maiden Rock, WI at the Smiling Pelican Bakery!) at almost every stop.
So the rule is, there is no rule. Feel free to modify your behavior for the ride you're on, keeping in mind your goals (if any), and the feelings of others in your group (if any). Wait . . . ah, I mean, if there are others in your group, not if the others have any feelings . . .
Rick / OCRR