I believe adhoc service is requested by customer, depends on when they required the jobs to be done.
I would assume customer will call few days or 1 week in advanced?
In cases where they will pay, I believe we receive PO from customer, then only job will be opened and performed asap?
To answer to your question, in compliance perspective, anything warranty and contract, we need a 100% completion. We will also stick 30 days on adhoc, unless customer indicated they need it urgently or we know that the equipment has past due date.
Ideally, close the job as soon as it comes.