I take the foot ball cover off once in awhile and just power spray it with the rest of the bike. wait a little then ride it to shake the moisture out. looks brand new every time. Only thing Ive seen hurt a filter is time,after long periods of time anyfilter will decay and particules of itloosen and go intothe intake ect.
The stock SE air filter is washable according to Harley. I never tried to wash mine I threw it away and put in a K&N filter like it should of had tobegin with.
in my opinion, washable or not, they're junk... i learned the hard way..2k miles and the inner seal was coming off...but,,i think a year or so ago, HD changed to a paper filter....guess they wanted to generate more sales..