T1 doesn't charge but I have never cancelled except letting him know way ahead of time if I am going to be out of town. T2 and 3 are in the same practice where there is a "you may be charged" if cancelling without 24 hour notice. I don't think I have ever cancelled with either of them with less than 24 hours. They both have a waiting list so it's no sweat off their backs.

I definitely try to give as much notice as possible when I need to cancel due to travel or job. I think 3 days is reasonable if that is the case. But if I was going to be charged if I was ill, I would show up and hope they caught it,. Or better yet, that I puked in their office.

And a definite no if I had to have the same time every week or pay for it. But I don't mind switching days or times around. My schedule is pretty flexible.