Bathing your dog once or twice per month or even every other month is okay unless the dog is dirty and needs a bath more often.
I bathe my dog once per month unless he gets into some mud and gets really dirty then I bathe him more often then.
But once per month is enough baths for my dog and is enough bathing for most other dogs as well.
But if your dog has fleas then you might need to give them a flea bath once per week to keep the fleas off the dog but dogs don't need as many baths as us humans do.