Some funny responses here. NO ONE will be doing kung fu in the backcountry when its freezing out side, and one is otherwise trying to conserve resources(calories). When its truly cold, your either in all your layers, working/hiking(ie:burning resources so make it count..while ventilating said layers and trying to keep them dry), or in your bag and in your shelter. No inbetween.
I've been on countless solo week long deep winter backpacking trips, and the long winter nights are often the hardest thing to deal with. Plus you've got such a short day(9hrs?), your lucky to get more then 11-13 miles in even when your hiking in the dark that morning(with snow, cut that distance in half at best). This is just reality for the winter backpacking/mtneering.
Having said that, I always saved the ativities of cooking, drying any snow-wet gear, repairs of any kind, studying the topo map regarding the next days route(where next water sources are, how far and how much ascent, where lunch might be, etc), and whatever, all for after dark(5:30-6pm usually, when it gets COLDer fast) activities. I do these chores while in the comfort of my bag while inside my shelter and out of the winter elements. This saves resources(calories) while not exposing one self(and gear) needlessly to the possible extremes outside(winds, cold, snow, rain, etc. -nothing like having wetted out frozen solid shells like WPB jacket/pants, or worse..laying around inside your shelter while making sure your other gear doesn't get fouled also. plus wet gear gets heavy for the next days hike).
Also, a small digi cam is awesome at such times, because you can spend time that evening reviewing/reliving pics of that days hike, while in the comfort of your bag. Brings back memories that prolly wouldv'e been long gone otherwise.
If I do it right, by 9-pm-ish, I've finally calmed down my mind and body and can then sleep for the most part.
I stopped building fires years ago since I hike alot offtrail in the wilderness areas(fires are illegal there, plus its pretty hypocrital to demand a prestine backcountry campsite and then destroy it with an ugly firepit). Plus its a ton of work for something your gear should be doing(keeping you warm and cooking). Plus it gives your position away. Plus its terrible on your highend nylon/poly(plastic) layers and shelter regarding smoke and flying embers if your anywere near it for warmth or cooking. I'd rather be spending my resources doing other things.