I'm really surprised by the number of people who will routinely wait long periods of time. For me, the 20 min wait is assuming I've been notified of a delay. If there's no notification, 10 min is the max I'll wait. I wouldn't be willing to wait as a repeated occurrence because it would feel to me that I was being repeatedly disrespected. I had enough of that behavior growing up; don't need/want to accept more of it now. It's an issue of self-care and esteem that would undermine whatever therapeutic benefit I'd get from the therapy. (With non mental health providers, it's more consumer-driven for me). And I would not expect any provider to keep my appt if I were so late without explanation--and both my GP and dentist have policies to automatically cancel appts for patient lateness beyond 15 min. So to me it's an equal consideration.