The best indicator is when you can't zip the sleeping bag over your head. Then it is time to take the plunge. If you wear a fleece hat at night, over the ears, it seems to get you quite a bit more warmth, possibly delaying the plunge.
The itchies usually go away on day 4, and then you are ok. Assuming you are wearing Polypro underwear, you can rinse them, and dry them in a slight wind, and that will keep some odor down.
Moose hunting for 10 days down on the Tanana, out from Fairbanks, I finally broke down, and took a plunge in the Beaver pond on day 6. Yep, naked with all those beavers around....
It is like any dip in 32.0000001 degree water. It just takes your breath away.... I think there are some pictures, somewhere, but they are not suitable for Internet posting....
But, for 14 days, you might want to go take a bath. If you have excess room, and are not moving from base camp, throw a solar shower in, next to all the other stuff. Hot water would be the ultimate luxury.
If you don't have rain, hang the polypro underwear outside the tent at night. It scares the bears away, as they assume it is one of them, only much bigger, and fouler....
