Well they can bronch someone all day long, if the cystic already has PA, they will always have PA. Even oregano oil (and other essential oils) won't be able to 100% get rid of PA. When someone cultures and "shows no sign of PA" after whatever treatment to combat PA (even oregano oil), it's because the PA levels are drastically reduced, but not eliminated. You are talking about microscopic life forms with the best place in the human body to hide in.
As far as an annual bronch, no not me. Research in aussie land might show that it is beneficial in early diagnosis means, but the procedure itself is also very invasive, and can cause problems in itself. I've personally never had a bronch, but i've known others who have, and even under anesthetic they have said it completely sucked (some said it was horrible). What is the bronch going to show you besides what common sense, deductive logic, medical training, CF training, and medical personel with experience dealing with CF infection can find on their own? You can go quite a while without colonizing PA as a cystic (I went till I was in my early teens), but once you got it, nothing is going to 100% remove it, it's with you for life. You can only use what works for you to keep your bugs as low as possible.