I would wait up to 30 min for my current T. In almost 2 years, the longest I’ve ever had to wait for him was 10 min, and that happened maybe 1-2 times and he apologized. He is always right on time or a couple min past (which I don’t even count as late in my mind), so if he left me waiting with no communication, I’d know it was for something serious and I wouldn’t be mad.