[Delphinus]

I used to use the felt socks and the only way I could get them clean was the washing-machine-with-a-little-bleach method. I have since switched to the mesh based socks (same micron size). I only use the felt socks now if I have a particular situation that requires extra mechanical filtration. With the mesh socks I only need to rinse them well at the sink, then I sit them in a small bucket of water with a tiny bit of vinegar for a day or so. Then they're good to go again.

As for how often to clean socks ... you can't really put a schedule to it. They'll tell you when they need to be cleaned. (ie., when they're overflowing). Can be anywhere from daily to weekly or anywhere in between depending on your tank.