Parking RV overnight at trailheads within national parks?

Acei wrote:
So are you allowed to leave your campsite with your RV parked in it for more than 24 hours while you are backpack camping in the trails?

The parks I've stayed in basically didn't care if you were at the campsite or not as long as you'd paid for the spot. But I'd check with the Ranger or Campground Host before doing this if you planned on being away for more than the day.