Well I do something rather unorthadox, maybe. I hike in the heaviest wool sweater I can wear that isn't too warm on the nice days when I wear it without a skin layer or wind layer. When it does get cooler or windier or if I slow down or stop, then I put on my skin layer under and/or my wind layer over. If it is winter and the temperature might really plunge then I might carry an extra fleece layer also, which goes over the sweater but under the wind layer. Sometime the fleece layer over the wool sweater instead of the wind layer over. Depends on what I am doing in terms of keeping rain or snow off or trying to dry the wool layer out some. 80-90% of the time while hiking its just the wool sweater with nothing under or over it. Hats and mitts and leg layers are other variables. In snow I might overdress my legs before I add layers to my body. When not in snow I tend to undress my legs, so maybe more layers up top if I'm not working too hard. I've been trying out wool pants recently, using them like the sweater, 90% of time with nothing over and nothing under but boxers.