Dressing for a ski tour isn’t a simple matter of just putting on the same clothes every day, regardless of conditions. At least it isn’t for me. I guess you could put on the same clothes, but they’d get rather stinky, and you’d likely not be super comfortable.
Warm days can be the most challenging because you’re likely to sweat on the hike, but “warm” is a relative term, and as soon as you stop moving, it won’t feel warm for very long.
Really cold days can also be challenging, as there’s not a lot you can do to mix up what’s on your feet, and aside from growing a beard, there’s no good option for keeping your face warm. And since you can’t grow a beard on your nose, and at least 50% of the population can’t grow one at all (or is forbidden from doing so by their better half), a beard is at best a half solution.
One year ago, I wrote a review (at the time quite preliminary) of the Smartwool NTS (Next to Skin) midweight baselayer. And regardless of what the weather is going to be like, I find this setup is my preferred first layer, especially on the long tours when staying comfortable for several hours is the most challenging.
The wool is great for minimizing the “swampy” feeling most clothing gets when it’s sweaty. It seems to do a better job of insulating when wet than synthetics, and it just feels warmer on the really cold days. If it’s warm, I hike with just the baselayer on top, no jacket until it’s time to ski. Cold days, I’ll put on a softshell for the hike and then add another layer for the descent. Even if it’s snowing lightly and I don’t have a jacket on, getting wet doesn’t seem to be a problem.
In fairness, Enel pointed out in the comments of my post a year ago that there are other companies making great stuff out of wool. But after a year of heavy use, I have no complaints about the construction or performance of my Smartwool.