My T has the 50-minute hour and it works well for me (and him too, I suppose). Although it does take me 20-30 minutes to warm up and really settle in, I think I tend to get to my limit of what I can tolerate emotionally by 45 minutes. Then we spend a few minutes winding down.

I think T spends his 10 minutes between clients doing process notes, running down the hall to the restroom, getting water, and stretching before asking the new client in. I think he needs a brain break between such blocks of intensity (I would, at any rate).