Here is a question, might as well go in this thread...

1. How much clothing for neck, face area?
A1. Some but less than rest of body.
A2. As much thickness as rest of body.
A3. Slightly more than rest of body, except for mouth/eyes.

I am not asking so much about how much is usually worn, but how much is carried, for the extreme conditions of that trip. If you were wearing it all, how much would the face/neck area be covered compared to the rest of the body, either sleeping or awake and camping, or perhaps even while moving at an energy comserving trudge.

In theory, the skin temperature in this area is the highest on the body, rarely falling below 93F, some extremities can vasoconstrict to 73F surface temp and still be comfortable. I thing beside having to breath and see, the face and neck area are very important for thermoregulation. So on one hand when its very cold you would cover them slightly more than average clothing thickness because the skin temp is higher. On the other hand, because you always need some thermoregulative control, it is useful if this area is always slightly under-dressed relative to the rest of the body, even when sleeping.

So I think the answer is A1.
Especially in winter, the answer is A1, less than average.
During summer the answer might be A3, to save weight.
I suppose that means during Spring/Fall it might be A2, same as rest of body..