It's Friday afternoon, and you're able to get out of the office a little early. As you are headed home, your spouse calls and asks you to stop at the grocery store. You're given a list—a short one you can handle!
So you go to the store and find the items without having to ask anybody for help. You walk up to the checkout counter and put the food on the moving belt. The clerk hands you a check tag and tells you to come back in three hours after they have everything added up. When you return, you will get in line a second time, pay and then receive your food. You calmly smile, say thank you and go to Starbucks to get a cup of coffee to begin the three-hour wait.
What? It doesn't work that way? Would you mind if it did?
How long do you make your customers wait for their repair invoices? Is the process different than going to the grocery store? Your customers don't think so, and they only tolerate the wait for the same reason you would be sitting at Starbucks—every other grocery store is just as slow at adding up the bill.