That makes no sense to me because when I arrange for service at the local RV dealer we sort out what I going to have done, they order any needed parts, and when all parts are in we schedule a day for service. I either bring it in that morning, or drop it off the night before. Same with the Ford dealer on drivetrain work, my tire and alignment guy on chassis work.
I do have to be flexible about the schedule, and it can interrupt plans to use the RV but it means that when they can't get to the job for two days, or three weeks, or whatever, it means I have what use I can make of the RV, it is not sitting at their place for that time.
Dropping it off, letting it sit, is just asking for a longer wait. Unscheduled work, somebody's "emergency" or work a dealer needs to close a sale or get rid of an irate customer, will all be slipped in ahead of you, your jibs just gets pushed back in the queue. If a service place is workingme that way, I'll find a new service place.