dude when i was in the army, my motto was 'sleep when you can'. if you are sitting around for hours doing nothing, then sleep and work something out with your buddies so everyone can get in on this and not get in trouble. if you are in the field (not deployed) and they have you on some retarded LPOP all night, switch off sleeping with the dude you are with, there is no reason for both of you to be awake. anytime else in the field too, no reason for two people to be doing one mans work. take turns sleeping.
it all comes and goes though, i remember days being so tired from no sleep and then i also remember days where i had slept so much and couldnt sleep anymore and was bored out of my mind.
oh well. good luck!