I had a couple of regs I had to cut off, both for the exact time reason. Time scamming. I'm pretty chilled about potentially running over, but there comes a limit. One wanted evenings and overnights for the cost of a couple of hours, the other wanted 2 or 3 hours for the cost of half an hour.
The latter really peeved me off, pressing for constant messaging, whining how he could only afford to see me once a week but not if I charged him the full rate for the time. Not my problem. Eventually I snapped and told him he wasn't welcome anymore.
I don't mind running long if we're just chatting and hanging, but not if you expect me to keep shagging. And especially not when you're asking for time during the work day, I have a day job, don't fuck with it.