Take em out!
I had a similar problem with my windows working intermittently. I took the switches out and cleaned up the contacts inside with a Qtip. Reinstalled them and have had no problems since.
You probably have a layer of dried root beer/sugar coating the contacts of your switch. Take em out and clean 'em up with some WD40 and you ought to be good.
Only thing is the switch itself is a little worn from constant use. Anyone know where I can get a new rocker for the switch? I don't need new switches, Just interested in cosmetic maintenenance.