When you're going to be productive you should get some rest. With a small nap consecutively I've noticed:
I went from 70s to 90s-95s in wordament (my knowledge of words obviously couldn't change in that time span)
My score in COD went from 1.1 to 3.2 KDR (Nothing changed except my competence after rest. when tired, I score far below what I consider acceptable to find the experience enjoyable, and it signals to me that I need to give it up and get rest)
These are my two basic findings. two different parts of the brain and they both require some rest before getting to their best! I'm sure the rest of our brains need the defrag too. Be my guest to point out the biology I'm not very adept at that, only first year bio under my belt. However I've noticed it's a constant pattern so that is indisputable in my books
GET SOME REST! IT MATTERS!
I was going to post this, but you beat me to it. also, if you get 8hours of sleep per night, your memory improves, you're not as 'groggy' throughout the day, and you're dependency on Caffeine/Alcohol/Sugar etc depletes almost immediately. There was a study done where a group of people were made to sleep 8hours a night for 30days, and they noticed changes in their routine and lifestyle almost immediately.
Ill edit my comment to show my source once I find it.