Also I don't think that Elon musk sleeps only 4 hours a day. He has a lot of people who are doing the work for him.

Here, I found that quote for you so that there are no more doubts. Wink

Elon Musk: "I sleep 'about 6 hours' a night – 'I tried less, but total productivity decreases'"
https://www.cnbc.com/2021/02/12/elon-musk-ceo-of-tesla-spacex-on-getting-six-hours-of-sleep.html

I am also somewhere in that rank. 6-7 hours of sleep a day is more than enough for me.