I don't think that it matters as much to them as it does to us in terms of cumming. For me that blessed moment might happen once or twice a week. For them it's at least a few times a day.
They know that our satisfaction comes from them being satisfied, which is why there's those fake moans and sighs. And jeez, there are the ones that everyone wants who cums every time. June at MetroGirls has classy, stunning visuals to this effect. I haven't seen animation like this since Ren and Stimpy.
I stopped thinking about it years ago, and when I did so I found that the overall experience was far more enjoyable for both of us. Their sense of satisfaction with a client is unique and personal, and it's less about a powerful performance and more about having a connection and feeling comfortable.
They're not lovers. They won't leave you after a few dates if you don't measure up. In fact, they've just left you for another client 5 minutes after you left.