Jones gets a weekly bath right now. He's still in puppy coat, so it might change as he get's older, but he too gets disgustingly filthy from being out and about.
I use conditioner every time (I also use Earthbath or BuddyWash diluted) and save the shampoo (which is an oatmeal shampoo as well) for every other week. I don't want to dry his skin out really, his coat is fantastic, but the skin is what I worry about. So far it's working, and he still hates baths, lol, but he has to have them or he's too gross for words