Well, my sessions run a little long since September. But what I would do is after you've blown your load is rest for 5 minutes, clean up go back to the bedroom and DATY or foreplay and take a dildo to her ass until you are satisfied with the show. Leave when both parties have felt the time is up.
I generally take my clues from the client, you know, if he gets to go shower afterwards or anything else like it.