Phil, how can you expect such a sense of reason when I bet you half the people stay in service while in the shop, hoping any load they get works with the shop departure.
It has been over a year since Diane and I left FedEx Custom Critical for Landstar. I forgot about the FedEx dispatch system. So yes, depending on one's carrier, the approach to in service or out of service may differ.
At Landstar, there is no penalty for going out of service. You don't lose dwell time because there is none to lose. If you are in service, you are in service. If you are not, you are not. It's that simple. When you come back into service, your truck appears on the board, no different than if you had never gone out of service, or if you had stayed in for an hour, day, month or more. There is no such thing as dwell time at Landstar; none to build, none to lose. Consequently, we don't have to lie to our carrier about our availability status to preserve our place in a que.
So, with that dispatch system in mind, if Diane and I are not available to run when a call comes in, we go out of service. It is not fair to agents to be unavailable but to show yourself as available. You are wasting their time by forcing them to make a call.
For something like an oil change or truck wash, we stay in service. But if it is a longer repair, we go out. We risk losing a load that an agent might call on for a pick up the next day, but the freight has been busy enough so that is not an issue.
Also, as the agents have gotten to know us over the last year or so, some will call us days in advance looking to snag our truck before they look for others. They do that because they know we are reliable and because we have shown them the respect of not playing games with their time and our availability status.
You asked, "How can you expect such a sense of reason ... ?" An expediter can be as reasonable as the dispatch system he or she works under. With FedEx, a dwell-time incentive is built in to lie about your availability status. No such incentive exists at Landstar.