Now for the other side of the coin. I used to book my shop at 7 hours/day per mechanic. This would leave plenty of time for additional repairs that the owner thought of the night before. It would leave time for some, not always all, of the additional repairs that the customer did not know they needed. It left us time to be thorough and conscientious about the repairs we were doing.
9AM rolls around, the doors have been open since 7AM, and one of the 6 customers scheduled has shown up. No calls, no contact at all. Then the next day everyone scheduled shows up and some of the a$%^oles from the day before show and expect their car by 5PM. When you tell them it is not going to happen they go ballistic. As a shop owner you can give some customers a $100.00 bill when they walk in, kiss their butt when they leave and they still are not happy. This is a very small percentage of customers but they are the ones that cause a good deal of your repair scheduling issues. A business owner can not depend on everyone showing up when they say they will and has to make adjustments for the clueless. I stocked a lot of parts because I was a vehicle specific repair facility but the shops that work on anything; RV, car or truck, can not do this and become dependent on their suppliers to get them parts in a timely manner. This also does not usually happen.
Good Luck but quit blaming the shop. One bit of attitude and the incentive to make you satisfied goes out the window.
Randy