When I am not bivy hunting I do just about what EKM states. I hunted a late season mulie hunt last year and got snowed on heavily with cold temps. I was nice and toasty. I also put a tarp over the tent linched between two trees. That method is alot cheaper and easy for 1 guy to set up if needed. If you use a cot in cold weather, make sure that you have some type of thermarest pad or equal to keep the cold air from circulating underneath, or you will get cold even with the best of bags.....