I live in the Sierra Nevada mountains in CA, and bought these to go under my work pants.  They work great!  Keep me warm, they don't ride or cling, or rip my leg hair out (I'm part sasquatch in that regard).

I will be buying 2 more on my next paycheck.  I'd say you can get away with wearing them 2-3 days straight assuming you wear some other underware with them (and swap those others out daily).  Just sayin. ;)