Question: I can't stay in house much more this winter I need to go on longer hikes.

I am used to longer hikes up to 14 days, but not during the winter. I want to do 1-5 day hikes in winter in dry weather, temperatures: - 12C(10F) to +5C(41F). The temperatues will be mostly 0 to -5 degrees Celsuis. There will be snow of course and I will have to use snowshoes from time to time,...

Now for 1 day winter hikes I use multi layers with soft shell on top, depends,.. I don't know if I should buy light down jacket, or a polyester one? I have no idea how down jackets keep up in case snow keeps falling from trees(does down get wet?) on you and jacket and how much do down jackets get wet from sweating? They say if down gets wet it is not good, but don't know what to expect in my case. I will carry up till 13 kg backpack. I don't know how much do these light down jackets handle weight and shoulder straps in practice?

What do you think, what are your experiences?

Answer: 
Down has worked well for me. My experience includes fall hiking at medium altitudes (10,000 to 12,000 feet), hence snow on the ground and snow falling. I've always had a down jacket with a water repellent outer surface, plus a water-proof poncho for rain or wet-snow conditions. The heavier and/or wetter the snow, the more often you have to brush the snow off your jacket, but moisture from snow has not soaked through the water-repellent surface plus poncho. The down itself has not got wet, or at least not damp enough to notice any lessening of insulation.

Caveat: My experience is fall, not winter, and where I hike there is rarely more than two consecutive days with snow or rain, and without sun in the fall.

I am sensitive to cold, and no fleece, even with multiple layers underneath, has ever been warm enough for me at the lower end of your temperature range, especially if there is wind.

You have more to fear at the upper end of your range, where there could be wet snow or even rain or some unholy mixture of the two. Thus, a good poncho is a must.

Your under-layers should absorb your sweat, and if they don't, take off something, either the jacket or one of your underlayers.

As for abrasion of the straps on the jacket, It hasn't happened to me, but I have always had a sturdy jacket. And, with a light pack (you say 13 kg), you might be able to wear the pack under your jacket if the jacket is loose; I have done that to keep a day-hiker dry.

Good hiking and banish that cabin fever!!
My experience is in the UK. Your problem isn't the -5, it's the 0. Once the temperature freezes and stays there, all the humidity drops out of the air. Above or close to zero, you've got general dampness to deal with, and down becomes much less effective when it's damp. If you're doing multi-day hikes where there isn't an opportunity to dry clothes overnight, this is a real problem, because *everything* gets damp.

Also on that note, get yourself off the tent floor as far as you can. Z-Rest type pads are great for this, because airflow under the pad helps to stop the tent floor getting damp.