Always on longhauls.
Ya know how your shoes are tight when you put them back on. Not so with socks.
I'm using basic support hose purchased and Walgreens.
There isn't a logical reason not to wear them really.
Mine are like black dress socks. I leave them on until I check-in and shower. (at hotel after flight)
Feet and legs in great shape.
-Scho

PS: These are the ones. (seems like black or navy for men, over the calf)
http://www.walgreens.com/search/resu...on%20stockings