How often should you bathe a poodle?

A coat that never sheds is a coat that mats instead.

A poodle's coat grows continuously, like human hair, and the hairs that die do not fall to the floor. They stay caught in the living coat, and every day of wear, the collar, the harness, a good roll in the grass, twists them a little tighter around their neighbors. That is a mat: not dirt, just trapped dead hair felting together. It is why the interval is every 3 to 4 weeks, the highest of any coat type, and why the schedule compounds. Skip one cycle and you have not fallen one bath behind, you have given every small tangle six to eight weeks to tighten into felt that no brush can save. Maltese and Shih Tzus run on exactly the same clock, because silky and long coats mat by the same mechanism the curl does.

The bath itself has an order of operations. Brush and comb to the skin first, because water is not neutral to a mat: a wet mat shrinks as it dries and pulls tighter, which is how a home bath turns a manageable tangle into a solid pelt. Then wash, then dry with moving air while brushing the coat straight, because a curly coat left to air-dry curls around its own tangles and sets them. Between professional haircuts, a maintenance bath at the halfway point, around week 3 or 4 of a 6 to 8 week clip cycle, is what protects the haircut you already paid for. White-faced Maltese and Shih Tzus get one extra line item: a daily wipe under the eyes so tear stains never get the chance to set.