Well, having had the car for 18 months now, I have reduced to doing it once a week on a Saturday morning, however up until now I have been doing it twice a week (Wednesday late afternoon/evening) and Saturday morning. It is white... (trying to justify it)
when I first got the car It was everytime was dirty especially the alloys as they are white, now once a week now ive clayed polished and waxed it including the wheels much easier to keep on top of the dirt the inside is once a week aswell
A full wash inside and out every weekend regardless of the weather, includes pre-wash snow foam etc etc. Then every 4 months ill give it a full detail and seal the bodywork. A full detail normally takes me a full weekend. It baffles me why people leave there cars dirty all winter then expect them to come up nice when they finally wash them again. The salt and grit is too bad for your car to leave it that long.