I agree with breaking it up into smaller parts. I see a century as two 50-mile rides. Since my bike is slow (or, if you ask her, her engine is slow!), a century would (and did) take me 10 hours. That's a LONG time to be on a bike. All my long rides, the century as well as the 10-day trip to Omaha and back, were done with plenty of breaks.
One lesson I learned is if you stop for a meal, you need extra time after you've finished eating to digest. That's probably true of snacks as well.
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike