I dont have a set amount of time I wait. some days Im impatient and right on the dot check in with the receptionist 1. to make sure I have the right day and time and 2 to find out if the therapist is running late.

Usually if a therapist is later than a few minutes they call in to their receptionist to find out if their next client is waiting. at least mine usually does.

I sometimes will call the day before my appointment (with in the 24 hour window my insurance company requires of me any time I need to cancel. I will leave a quick message verifying the date and time of my appointment, that way my treatment provider knows I will be there on time. my therapist also notifies me when they may have a problem on their end that may affect whether I have to wait or cancel.