I am typically very laid-back about time, but I do take issue with the expectation that quality service = extra time. Not that I don't sometimes do it, but I reserve the right to a hard "time's up." Very seldom will those words cross my lips, but there are many reasons why I may need things to end at the scheduled time, and none of them justify someone complaining on a review board that their session ended only 5min after it was supposed to.
I could need to text my safety, have a personal appointment, a work one (they are never back-to-back or anywhere close, but I do like to take a decent amount of time preparing), I could be asserting my boundaries with someone who I can tell has been trying to push them, I could have studying to get done. Hell, I could just be holding back a wicked fart.
The point is, my time is my time, and so long as something I have done has not cost someone theirs, it is my prerogative to extend it to someone else. Not doing so should not affect the perception of my quality of service I provide when I am on yours.
Not that I think that this is your intention in saying this, but I have noticed this attitude from others, and it vexes me so.