One doesn't want his store to look way out of line with his competitor. Likely, the one that maximizes its time by billing for the largest percentage of those 60 available hours. To look at it another way, each tech at the store has the potential of producing 60 billable hours. The healthier the business, the closer each tech is to delivering 60 hours of paid labor per week. The more productive a tech is, the more billable hours he logs.
Productivity seems to be a relatively obvious aspect of running a service department.
In my opinion, a crucial but less obvious factor is the financial impact of a comeback. Everyone understands they can't charge for a comeback. But they miss the fact that correcting comebacks actually costs twice the time they think it does. Also, we'll assume there's no backup, such as a labor warranty, paying for the tech 's time. The store's first loss was the two hours of free labor required to correct the job.