For me (and the majority here, i guess), the quality of a session matters, not the quantity (time). It is a game with its own dynamics; i like going with the flow created by my mistress. And accidently(?), the best point ending the session sometimes 'comes' a little too early.

This depends IMHO also on the kind of play; if its focus is on e.g. punishment / whipping / caning, it's all in the hands of the domme. But constant erotic edging, interrupted with (growing) pain, can lead to a sudden end, allthough you try everything to prevent this happen.

But as i have had quite an amount of sessions with my mistress already, she once gave me some money back or told me once to give her a little less next time. Keeps me a happy camper and keep on requesting ongoing service. This kind of trust can evolve after a couple of months / years.