Owning a service center, albiet a different service, I always took into account the urgency of the customer. I knew which units I could work around and which ones were needed immediately. A recent breakdown found us at a Cummins dealership that did just that and went out of their way to get us back on the road. Albany New York Cummins. Fantastic folks and service.
One thing I would like to suggest to the service departments is to have the techs talk to the customers. Yeah I know, they are not the best public relations folks but they can learn to be. They can play "20 questions" with the customer and dig out critical information the service writer just does not think of or is inexperienced.
When we had a "drive in", I would pull a tech and have them talk to the customer or I would since I am a qualified tech. This saved a lot of misery and gave confidence to the customer that we really do care and getting the facts is important. Sometimes rephrasing a question to a customer will bring out a tid bit of information that is the real clue.