We used our limo after the ceremony to take everyone to DTD for our reception luncheon at Portobello (we actually used two shifts since we had 14 people total). Anyway, that might be an idea for you, so you don't end up not using it at all. The 4 hours was plenty of time for them to pick up first round of guests, drop them off, pick up second round of guests, drop them off, then come back afterward and repeat the whole process again. Just an idea!