I often entered zombie mode in college. I now work for a tiny company that lets me choose my hours and even let me set up a place to sleep in the conference room. Because of their flexibility, I was able to take up polyphasic sleep. Now, I never have a time of day that I get that tired, and I don't miss it. It always left me with a hollow/sick feeling the next day.

The amount of sleep required by a person to feel fully rested (assuming you get all of your sleep in 1 large chunk) makes a very nice bell curve with about 2% of people needing less than 4 hours and 2% needing about 12 hours. People on the left side tend to call people on the right lazy, but it isn't something controllable or trainable. Most of the evidence points to it being a nature rather than nurture type of thing. I fall in the 9-hour category, which didn't leave me as much time as I liked in my day, so I moved over to the Uberman sleep schedule. I was able to do this because I work at a small company whose conference room now doubles as my nap room. -- TM