I have two Australian Shepherds. And they only get a bath when neccessary. Meaning when they smell really bad, or when their coat is so dirty, it won't get clean after a good brush.
It would probably come down to about 2 or 3 times a year.
But my dogs love to swim, so that really helps a lot.
I always say, I have selfcleaning dogs
No matter how dirty they look, as soon as they are dry, they are clean again.
When I do wash them, I use a dog shampoo. And for Jinx a special shampoo for her white parts, as that tends to go a bit yellowish.