I am generally willing to wait 30 mins at appointments if there is not a particularly strong (positive or negative) motivation factor. I have waited >2hrs for a doctor (repeatedly) and ~1 hr for a hair stylist - in both cases, I knew them and was quite confident that the wait would be worth the end result. I think waiting that amount of time can ultimately be more economical than rescheduling, having to deal with the frustration of it's not being done and having to go back for the same thing. I would not wait more than 10 mins if someone previously demonstrated repeated unreliability and useless work. So, it depends.