In a perfect world, a load-in/load-out that goes well is a positive experience for all involved. When they go bad, it's a special foray into one of Dante's circles of hell. The gig, be it a stadium concert tour, bus-and-truck theatrical, or even an opera, can quickly transform into a very unpleasant event.
Part of the designer's job is to design the show so that it can be physically set up in all of the specific houses that the tour will be visiting.
Jim van Bergen