How often do underwear and socks require biasing?
Depends on the amount of leakage.
I spring the extra $ for the black ones for that very reason. NOS Calvin Kleins are superior in every respect to anything being made currently. You'd have to spend at least three times the $ to equal the performance. I bias my own tube every so often, but always prefer to let my wife do that as she is much more skilled at it than me.
Marco