I've done all day Zoom/VC mobs, and that sounds exhausting as hell to me. Different strokes and all, but programming this way really takes the fun out of it.
We thought it was going to be exhausting like you said, and one of our guys even brought up that he was very introverted and didn't know if he would be able to do this. To our surprise, the days go by faster (not just because they are shorter), we get done with more work than we did before, and although yes we are tired after working all day, we all look forward to doing it again the next day.
It's true, mobbing isn't for everyone. But for us it couldn't have worked out better.