How many days in the week are recommend to do deep work ?

Becky J.
It depends on the needs. As for work related focus, everyday that work. Because as a manager of 10 employees and consumed by 4-5 hours of meetings daily and to reflect and prepare for them. I like to block on my calendar an hour at the beginning and end of day for the focused time.
As for deep work on personal at home items I like once a month for several hours to focus on the task.
If your a student you might want to consider your learn style and do you learn best right after class when its fresh on your mind or after a couple of days? Depending on the answer I recommend an hour or two of focus on that material.

Houda Q.
As many as you feel you need to. Don't over work though because it's just gonna push you to stop the first time you encounter a problem. So it depends on your schedule and what you aim to achieve with that deep work.
And to properly answer your question, I think 3 times a week is pretty good (not too little not too much). But as I said, see for yourself.