I've found its worthwhile changing into dry thermals for sleeping in. Anything I've been wearing during the day will have accumulated some dampness which isn't noticeable but definitely chills down at night.
Fantastic thread Scott! Right Grahamfitter. I'm only to #704 and had to post. This is acceptable and should be comfortable with a proper bag. Moisture on clothing is the enemy in extreme cold. Per my Army training playing in the snow 8+ feet deep in -52 degree weather with the 10th Mountain Division. Bad idea to wear all your day clothes to bed, you can freeze from the damp clothing even with a coat/parka, the next day, that could be 28-30 hours in the same clothes the next morning and they will be damp even if you don't feel it the night before. Temp and humidity both play a role. It also depends on how much you sweat in your bag too, if you're too warm and forcing yourself (psychologically) to stay covered up, you'll sweat. Clean and dry thermal cotton long johns are good to hit the sack in, if you wake up damp, change in you bag, then get dressed. Keeping clothes in the bag but not against your body, don't breath on them, that keeps clothes warm enough. How can you tell? Sit up in your bag and expose your upper body, if you start chilling on you back, chest and arms in a few seconds, you're damp.
I know clothes have changed since I charged up hills but the principles are still valid. Wool is still my friend. I think the Army winter survival manual for Artic conditions, FM something, is available and unclassified, not sure now, but you can check through Govt. Publications.
Edited, finished now, an all day read LOL. Fantastic doesn't describe this adventure, lucky you! Ought to make a movie! Hope you got enough tape.
Good question......what's next, you're too young to stop after this one?