If someone is there to put stuff on a site, someone is there. If someone is there, the site is occupied. If someone is not there but coming back soon, the site is occupied.
When I was a kid, we tent camped every 4th of July week in a national forest. It took dad three or four trips (30-40 minutes one way) to fill the family sedan with all of the stuff needed to sustain 4 kids and 2 adults for our week's vacation. The next to last trip, he took mom and my younger brother while the other 3 of us stayed at home packing our stuff. The last trip, he took the final 3 kids, our stuff, and our bikes. A week later, it was the same thing in reverse. I think it took one trip less coming home as we had eaten all of the food! I do remember a friend of his with a pickup truck helped one year and we did it all in one trip (two vehicles).
I can't tell you how disappointed we would have been had dad's claim not been respected by other campers. We didn't have a camper or a vehicle that could haul all of our gear and all of the kids but we sure did enjoy our week of camping.
40 years later, Mom and Dad will spend Memorial Day weekend camping with me - they in one travel trailer, my partner and me in another...both on leased lots, so we don't have to worry about when we get there!