A Portmanteau of the words "sleep" and "vacation".
Sleepation is a period of time completely dedicated to recovering sleep with short periods of wakefulness for eating,drinking(water),vitamin supplementation,hygiene,toilet trips and small periods of non intensive exercise.
It's when you feel like you've got too much work to go to bed, but you are too tired to get anything done. So you just surf the net and procrastinate until you can't stay awake anymore.
Joe: Dude how did your 3000 word essay go?
Tom: Well I managed to get half of it done yesterday, but then I got stuck in sleepytime limbo and just stayed awake the whole night browsing through facebook...