on page 2 of the thread linked above xw5's linked "College Callgirls Top Ten Tips to Get Him to Hurry the Hell Up and Cum Already" had some great ideas and a hilarious turn of phrase :-) Also, if you allow clients to cum multiple times during a booking, maybe remind him he can cum more than once. If he's the type who feels the need to try and set an endurance record every time, he'll most likely take this as a challenge to cum as soon as he can, take a break, then try to get hard and go again. Even if he succeeds, you'll get to take a rest before round 2. I find with most guys it's either their nipples, balls or asshole that's the magic button to make them cum quicker from oral. Failing all 3, if my jaws locking up it's time to switch to a handjob with baby oil