I'm not quite yet in your age category, but I've kept a pee bottle with me at night since my 20's. - and just dump it out in the morning and rinse it out. A 750 ml gatorade bottle or something like that. Perfectly sanitary. While it may sound strange, those of us who have spent a lot of time out
in very cold conditions take a more practical approach of "why freeze?" - and at that point, the heck with it, even in nicer condiitons. It's easy in a tent. It's somewhat more challenging to use in a hammock, but possible <img src="/forums/images/graemlins/smile.gif" alt="" />