In 40 years of RV ownership I have never left an RV at the shop overnight. I do most of the repairs myself but on the things I could not do I made an appointment with a clear understanding of how long it would take to make the repair. I drop it off in the morning and pick it up in the afternoon. If they need parts I have them call me when the parts arrive and I make another appointment to have them installed. I have always kept my RV's inside a covered building and I don't want it sitting at the dealership outside in the elements with an invitation on the door for someone to remove items that appeal to them. If the shop will not do it this way then I go to one that will.
I read on this forum where people have left their RV at the dealership for months waiting on repair. I would never accept this. If it were a warranty repair then I would be on the phone with the manufacture making arrangements to have the work completed elsewhere or by a mobile tech.
The dealerships will do this if the customer allows it. If all the customers went elsewhere they would would either change their ways or go out of business. Just my 2 cents worth.