Let me rephrase -- I shoot a lot of Herters in Alaska throughout the winter, and have for years. I have never once had one "go bloop," indicating cold-affected powder, and I shoot clays in colder temps than I will hunt in.
I would say what is obvious is that their wads and powder are just fine.
I do like copper- or nickel-plated shot for minimizing feather-drag, so that is what I use hunting, but if Herters were all I had I would not blink.