Most trailheads are located at the top of a steep, narrow, twisty road which may or may not be paved. Not the best roads for an RV to navigate and forget the gas mileage. Consider having a car to commute to the trail heads with and leave the RV parked in one spot for as long as reasonable. 5 to 7 days is actually a lot of food to carry, 3-4 days is more manageable. It may not be reasonable to go back to the RV that often, but he could meet up with you at a midpoint to resupply a few more days of food before the trip back to the RV.