I guess I'll step in on this one. Taking my knowledge from years of motocross racing, these filters are made of the same type of foam and the same oil is used for them.
It's perfectly fine to clean them if you do it the correct way. Thinners and solvents will break down the foam. There are some solvents made specifically for air filter cleaning and those work fine, but aren't needed. I was all of my filters in the sink with soapy water. It easily breaks down the oil and gets everything out. I just soak it the filter wish dish soap and work it in really well then rinse it really well. Do not stretch or wring out the filters, it will tear the foam and break it down. Just a simple squeeze to get the majority of the water out is sufficient then let it air dry. If I'm in a hurry, I will throw them in the dryer for 5 or 10 minutes. I put them in a bag, oil them, and they are ready to go again.
As far as how often I change them, it depends on the track conditions. I always inspect it after every run and change as needed. For instance, yesterday I ran pre race practice then changed the filter before quals started. I ran all 3 of my quals, then changed it again before the main.