Brevets being what they are, I like to take two days off before one. One isn't likely to make a hard effort on a brevet unless one is an exceptional rider who will come in a couple hours before anyone else. Instead, what the average rider needs is completely topped up glycogen stores. So that last couple of days I'll keep calories about the same but shift them toward carbs. The day before, I'll drink two bottles of a sports drink like HEED or Cytomax to top up my water and electrolytes.
So it depends on how old you are and how quickly, in your experience, you recover completely from a ride.