So long as you are offering continuation of service for the full time, then I'd not worry about it too much. Regards longer bookings depends on what the guy wants, I often ask at the start can he perform more than once and that gives a good idea how quickly to go. I'll usually start with a lot of kissing and cuddling, if he wants to move quicker he'll usually say. I find majority of 90 minute/2 hour appointments want to spend first half hour snogging, followed by half an hour oral/foreplay/69, 15 minutes intercourse in a couple of positions, then 15 minutes chat and cuddle afterwards. Other guys want to get naked and into sex immediately, and get a couple of rounds of sex in with chatting/cuddling, playing with toys inbetween.
'Filling' time with chat isn't something I aim for, if that's what the client wants then fair enough, but until I know otherwise then he's paying for my intimate attentions!