My adult dogs get bathed every 4-5 months. I try to avoid drying out the natural oils in their skin. Most doodles clean themselves well, even the light colored ones.
Kali usually gets a bath ever couple of weeks. I try to let her go longer, but she swims most days and gets really stinky from playing at the beach. Sometimes we can make it longer with just a rinse in the shower, it helps get some of the gunk (and smell) out without using shampoo.