If you really like your wheels and want to keep them new looking longer don't go longer than 5k miles without a good cleaning front and back. Once the brake dust builds up on the wheels it is very difficult to remove completely. I use simple green on the back of my wheels at 5k interval but it is not a strong cleaner by any sense of the word so I don't know what to recommend that won't harm the finish. On the face of my wheels I use Meguiar's wash and wax both water and waterless, easy peasy to do on a regular basis.