I've had these for a month now, and I've worn them with my steel toe boots at -10F.  My feet were fine.  I have a pair of Red Wing boots that fits a little loosely around the ankle, and wearing these socks seems to help that out.

An added unintentional test was that the water pipes in my trailer broke and I used my laundry and some towels to clean up the water.  With these socks, I wrung them out and hung them in front of the heater.  By morning, they were good to go.