Totally agree, for me it doesn't matter if it's a physiological reaction to heat loss, or just all in my head. Either way getting up and going to pee helps me get back to sleep. As an added plus, after getting up and going to pee outside, getting back into a sleeping bag always feels great and makes me feel relatively warmer than I was before (again all in my head, but that's how I feel).keeping it in does compromise warmth despite what previous posters say - get your ar$se up out of the sack and go out and poke a yellow hole in the snow - seriously - you'll get back in the sack organized and sleep great
[/QUOTE]-- by the way, I've posted this many times before but, for great warmth below about 20 deg, I love to sleep with a hot water bottle - after dinner, boil your cook pot full and fill your nalgene -- don't cross-thread and seal tight - sleep with it in your crotch (or on your belly) - you will sleep great and have a bottle of water to drink (or make coffee with) in the morning.
Even though every experienced climber and winter backpacker I know swears by this method, I've never had the nerve to try it out due to my of spilling water in my sleeping bag. This winter I'm probably going to bite the bullet and give it a try, though I might add a couple of oatmeal packets to the water to minimize the possibility of leaking.
Any tips for not screwing this up?