I have used my kit foam filter for all of my miles. I do occasionally rinse it out and re-oil it with 10-30 oil.
I tried a thicker foam filter, but found it to constricting so went back to the thin one.
In one instance I used cheese cloth oiled with motor oil. Works well also, the dirt sticks to the oil, when it gets to dirty to breath, throw away and re-oil some cheese cloth. Not to many layers though, these little motors like free flowing air flow.