Every Sunday. Religiously
Front wheels get a spray with Meguiars Hot Wheels cleaner, and then a once-over with the sponge to remove the determined spots. Whole thing with Meguiars Gold Class, then chamois dry, including the door jambs, boot, and even under the bonnet.
I've just got a hold of some awesome wet-look polish from Meguiars too, so I look forward to putting that to good use.... later today, I suppose, hehe