Yeah I could never be on a video call for that long. There is a subprocess in my brain that starts running at 95% when I'm on a video call, like a kind of performance anxiety. I can deal with longer voice calls, but I can't really work during a call so it's only useful for syncing up. A call longer than an hour has probably become inefficient in some dimension.

Pair programming is quite intensive when done correctly. You build stamina with time. But even so, using the Pomodoro technique is the way forward. Someone driving for 20/25 minutes, then 5/10 rest, and switch the driver.

Even so, I will still not do it 8 hours a day. Probably 6, to give you time to do other stuff, like investigations, admin, ...

At one time in my career I pair programmed pretty much all day, every day for the better part of four years, with the same person. We started with an existing codebase, but even from the start most of the work we did was on new features.

It is intense, but--at least in my experience--it was also very productive. You basically can't/don't ever slack off. And I learned a lot from the other developer (mainly about various tools). Things that theoretically I could have learned on my own but in practice I probably never would have.

If I had it to do over again I would definitely choose to do it again.

Yep. If I have more than 2 hours of meetings in a day, I basically lose the entire day.

He was quite diligent about taking regular and appropriate breaks. Partly in response to having worked through too many lunches prior.

Brain sag still occurred though.