I always tell the service center when i schedule an appointment that I am a full-timer and have no other place to live. Nearly always, they accommodate me. Some service centers, especially factory service centers, also have parking lots and hookups so you can spend the night in your RV. And one advantage of factory service centers is that they tend to have parts available.
I think that dealers who take weeks and months to fix things are taking advantage of you. Obviously, they prefer to do work at their convenience, not yours, so you have to be insistent and clarify when you schedule.
I have only twice had to stay somewhere else while my rig was being fixed. Once was when it needed major warranty work on a soft floor that turned out to be a broken weld--needed to take slide out, remove linoleum and plywood floor, re-weld broken frame, replace plywood, and put new linoleum throughout motorhome. I rented a car and drove to my son's house for 10 days. Another time, I had slide work done and stayed one night in a hotel.
Also, one big tip: if something needs repair, ask if they have the part when you schedule. Often, waiting for parts is a major cause of delays. I have gone so far as to order a part myself and have it shipped to somewhere I can pick it up myself. That was for a non-essential item on a derivable rig. And I do use mobile repair people as well.