Depends too on the ride conditions. Judging by your avatar, if the ride is in Texas, I would imagine you'll need to make sure you keep hydrated. Have a large breakfast about three hours before the ride.

Here in the Pacific Northwest, I've been out for a couple of hours, maybe 45 to 55 km depending on the terrain, without carrying a bottle or food. After years of riding, you get used to going longer without eating or drinking. Might come from track racing, where you might be going 20 or 30 minutes at close to max, with no chance of consuming anything. But then between races you're downing quite a bit of sports drinks, hot tea, trail mix, etc.

When we're on the tandem, we sometimes go an hour to two, then stop at a cafe and sit out on the terrace with the bike leaning against the wrought-iron fence, and have a nice light lunch, then continue for another hour or two. You can carry this civilized approach to the organized events.

L.