according to the website, craft prowarm baselayers are for below 40 degree weather. I'm wondering what people's experience has been with prowarm and what kind of temps you would wear the ls shirt alone or with layers (and what kind of layers). this info would also be helpful for prozero and prozero extreme baselayers.
I can't comment on Pro Warm, but I have used Pro Zero for at least 20 years and I think they are fantastic. I love the longjohns, just add another pair if it gets colder. I have tried wearing 3 pairs but then it gets a little tight. The top can get smelly in the armpits if you sweat a lot, just wash them. They will last a long time, they just gets a little thinner. I just bought a new batch as I could poke my fist through the hole in the behind on three pairs. They have seen daily use in the colder months and it must have been at least five years since I last bought a pair. I didn't even recognize the name, they must have changed that sometime.
I've only the prowarm, having eschewed the prozero, and wear it with a LS jersey into the low 40s, and with a craft thermal jacket down to the high 20s, with an added LS jersey in temps below that. It's pretty warm, in other words, and something I like since it minimizes bulk.