I'm not sure if there is a set "cat bathing schedule" you should go by unless your specific cat has coat/skin needs that need to be met.
I think how often you bathe your cat is going to be an individual thing. It sounds like you have a bathing system down that works well for you.
My older, short haired orange tabby cat very seldom gets a bath, which is good cuz he HATES baths. I tend to just "wipe" him, similarly to what it sounds you do.
My 10 month old doll-faced persian gets an in-the-sink, sopping wet full fledged bath every 3 months or so, cuz his very long (7 inch long) fur tends to get into something about that frequently, plus it removes excess dead hair/oil from his fur. Luckily Windslow doesn't get rattled by baths.
Both of my cats are indoor cats too, by the way.