hmm.. I don't think friction has that much to do with it.. Sure you move at night, but not that much..
You could look at getting a case with a higher thread count, so it's softer, and wouldn't cause as much friction (if you have a paranoia about that)
I wouldn't say it would be remedied with a satin case, but it may help..
I honestly think the problem is remedied by a constant clean case every night or as aanabill stated, a clean cloth.
Within two nights or so, the oils from your hair and face can significantly build up and collect all sorts of things and by the third night, following any regimen isn't going to help if your sleeping on that!
Edited by Zefferson, 13 July 2013 - 08:09 PM.