The main reasons we found move-out to be a bit more stressful was that instead of our kids being excited for a new year, a new adventure, they are exhausted from finals and often a bit grouchy about coming home after a great year in college. In addition at move-out the kids are not always packed up as much as they could be so that adds to the work. And yes, they somehow accumulate more stuff as the year goes on. That said, just allow plenty of time and be sure to have enough space for stuff. My other advice is to keep smiling. (no matter how painful it is) and not to complain about how dirty the room might be.
And we always show up with a few boxes, black trash bags, and a swiffer (with many refills).