Chat and cuddle for a few minutes... kiss a bit. When you're getting down to business, find out what HE thinks is going to happen. I will literally say something like, "How many times do you think you'd like to cum tonight?" A typical guy will be happy to cum once, chat and cuddle while they rest up, go for round two, and then some wind-down chat and cuddle. He may have the idea that he can cum four times, although even if he does, it's very likely he won't be able to.
A lot of men book two hours because they're looking for something to eat up the time between dinner and sleeping that isn't watching television. They don't necessarily expect a two-hour porno session. I've even had guys realise they'd been overly ambitious and, after cumming once, just want to go to sleep! I make it clear that I'm happy to stay and cuddle, chat, watch telly, whatever. I may even say something like "Well, you've paid for two hours so I'm happy to just relax with you." This makes it clear that you respect their time and the money they've spent BUT that they're not getting a partial refund. (You may feel that you should give a partial refund if you only stay half the time or whatever, but that's your prerogative.)