A small percentage of people, usually men, can function fine on four/five hours of sleep night-after-night. If you're up for sixteen hours a day, you can get more done. You'll note that across different fields and professions, the highest-achievers tend to have this characteristic. This is one of the reasons I despise, "Work smart, not hard." The truth of the matter, which many don't want to hear, is that if you want to rise to the top of whatever you do for a living, you have to put in a ton of hours. People at the top of their fields have not and will never put in 40 hour work-weeks. They don't adhere to "work-life balance."