I bathe my dog a lot more frequently than others posting here, but not with a soap based shampoo. I have a groomers shampoo called HyLyt that my vet recommended. It's soap free and has moisturizers and fatty acids in it which is good for their skin, there is no limit to how often you can use it.
Once a week I take her to a doggie daycare, and half the time she comes back with a strong dog odor, so she gets bathed almost once a week with the HyLyt. Besides that I take her to the groomer only a few times a year where she gets an oatmeal shampoo and her nails, ears, and teeth cleaned.