It's up to you because everyone works differently.
The point is that you need to have some food on you because once you feel hungry it's too late.
Generally speaking, have a decent breakfast, and then for your first snack (maybe a couple of hours in) have complex carbs like a flapjack, meusli bar or energy bar (torq; powerbar etc). Do the same a couple of hours after that, and then get home on simple sugars like energy gels or jelly babies. Don't forget to drink plenty and take opportunities to refill your bottles.
For 70 miles I normally just have one lunch stop and that's it.
For anything over 80 I have a short break, then lunch, then another short break.