RE sleeping in game....
Typically I sleep in the field when I can (will be doing so again this weekend at Deadfall, woohoo!) but twice I've slept in a car. First time I did this was at first Op Rhino a year and a half ago and I regretted it as I missed a number of awesome firefights. Second time was at Shallow Lake as I was still nursing some injuries from a harsh bike accident. I wasn't proud of myself as while I slept in a comfy car my buddies slept on the ground in the cold.
Otherwise I've slept on the ground at past games, sometimes in a hole that I or someone else dug. All it usually takes is a good warm coat or a ranger blanket to keep you from getting too cold. I never really look forward to much comfort when this happens but usually by the time it does I'm too tired to care about how comfortable I am.
I've seen people pass out face down on the ground before, with one hand still clutching a gun. Again as Brian stated not exactly a recommended course of action, but it does look amusing!
Sometimes all it takes is your friends berating you a little to keep you going until the end of the game.