I've got some Smartwool socks that have been worn on many backpacking and hunting trips, still going strong. Have found I prefer Vermont Darn Tough socks though, toe area just fits my extra wide feet better. And have some Smartwool long johns that haven't been used much. And Icebreaker long johns, which is why the Smartwool hasn't been worn much, just like the Icebreaker more (and love Icebreaker 100% merino T's for hot weather hiking). For sleeping in my tent in sub zero, I have some Woolpower heavy weight long johns. Have only worn them during the day hunting once, too warm for temps in the teens. And too warm for sleeping except single digits or lower.
But, end of the day, I wear UA synthetics more than anything else. Just the right amount of insulation for me, for most winter days of coyote hunting. The lightweight merino isn't quite enough and the heavyweight is too much. Just of the stuff I own. Easier to wash the UA too.
For the temps mentioned here, 30's and 40's, I don't wear any base layer though. I'm still wearing a lot of cotton stuff at that temp.
- DAA