They're holding up awesomely.
I don't use anything but lukewarm water from the tap to spray them off. If I have time I let them air dry in the drainer. If not I use a blow drier w/defrost capability to blow them off. Never use direct heat on them since they're molded and not hard plastic.
So long as you remember this they should hold up for a long time. I've had these for almost a year now and they look almost brand spankin new. If I see they're getting a little dusty(due to the birds in the house) I brush them off with a soft bristle paintbrush when I'm bein lazy. I honestly probably should be rinsing these off twice a week.
Soon as I can afford more I'm gonna get the full kit so I can swap them out as needed.
For quite a while now, I have been using a vacum cleaner to vacum the dust off case filters and grills
A lot of people freak when I mention using a vacum cleaner anywhere near a computer, but I certainly don't use it inside the case or anywhere near any static-sensitive components. If I can pop off a grill first I will before vacuming it. It is just a very quick and easy way to remove the surface dust.
But it is no substitute for more thorough cleanings with damp cloths such as on fans where the dust often glues itself to the blades.
Then again, the water-washing method is probably best for the DEMCiflex filters