Walter asks, do you think it's possible to push past the four hour a day limit for deep work? Yeah, Walter, it's possible. The four hour limit comes from research of professional musicians. Four hours is roughly probably a cap on really intense deep work, but most knowledge workers don't get anywhere near that level of intensity.

So that number came from the study of I think it was professional violin players. You see similar numbers for professional chess players as well. They do very intense training where they're trying to solve puzzles. Here's a position puzzle, and it takes really intense concentration. There's only so much of that you can do, maybe around four hours.

Most people doing knowledge work are not anywhere at that level of intensity. What's actually happening in their brains, they're going up and down, focusing really hard, then relieving that pressure for a while, then focusing really hard. So yes, you could spend, and people do spend more than four hours working on things deep.

The only addendum I would add is why? I mean, if you're spending more than four hours locked in on one thing, really trying to push yourself past where you're getting good returns, the question is maybe you should just slow it down. Good work day after day after day, let that break up.

So yeah, you can do it, but I wouldn't build a professional strategy around, let me spend 10 hours a day working on one thing. I don't think you're going to end up in a much better place than spending three hours a day, but working on it day after day after day, that's probably going to get you to some better work.

And I don't know that you're going to save time heroically trying to fill your day anyways because that brain is going to tire out.