I'll generally just ask if a gentleman desires to "extend" if our time is up and he shows no intention of stopping the action. There's really no need to mention money specifically as anyone who plays in this realm knows that we charge for our time. Pretty simple.
Now, that's if and when I actually have the time to extend. I don't book appointments back-to-back but I do often need a good bit of time in between to clean up, eat something, relax, and refresh my mind before my next meeting. I don't think that the next guy deserves poor service because I'm distracted from not having enough time to reset between appointments, so sometimes I'm just not available to extend any given session. In this case, I will simply start getting dressed or ask if I can start the shower for my undoubtedly sweaty playmate.
