Strider gets bathed weekly. If I have access to a forced air dryer, it takes about an hour and a half. Otherwise he has to air dry and takes less time, but doesn't look as good afterward. I bathe him that often because he's a service dog. A lot of people in public don't want to smell a damp dog, and it's pretty damp around here so he needs to be extra clean.
Also, once a week was the magic number for keeping his dander down when I was taking care of a girl with severe dog allergies. She couldn't even pet a standard poodle, but had no problems hugging Strider with that bath regimen. It makes me feel better, like maybe we're causing less problems for people with allergies when we go places.
Kaia gets bathed when she's dirty. Which could be weekly, or a couple times a month depending on whether she has a wipe out moment through dog doo or not.