Depends on the situation. My it Ts have rarely been more than 5 minutes late. Once T and I had a miscimmunication on times so after 15 minutes I messaged her to say that I figured we miscommincated on a time (it was an added appointment on a Saturday.

There were a few over the years she was in with a patient and running late. I knew that she would only run late if there was either a major breakthrough or the client was struggling. So I waited patiently once for 20 minutes. She apologized profusely. Since she always went over on my appointment because I was her last appointment, I didn't mind at all.

Emdr T has only been a few minutes late 1x and again she was in with a client.