Exactly - if that is something you want, be clear with her from the start. Also, you better be damn confident that you can indeed get the second pop in. If not, then be clear that you are ok with stopping when time is up. As Patron states, when the appointment is outcall, the hour includes about 10 minutes of her showering and re-applying makeup.
The girl will be WAY more appreciative if you book her for 2 hours or even 90 minutes if you have your heart sent on MSOG.