As soon as I got mine home I removed the wheels, washed then sealed them with 3 coats of wheel wax. That was in December, even now they are clean after a blast with a pressure washer and a quick wash with car shampoo if necessary. Dry them afterwards to prevent water marks and they'll stay wonderfully clean and shiny. I'll repeat the above wax process as soon as the water beading decrease.
Detritus.