There is only one respiratory issue that I will treat for, and it's only if I can determine that it is indeed that issue-that is situational pneumonia. That means it's not contagious and for some reason, a spore or bacteria set up housekeeping in one bird's lungs and caused pneumonia in that bird. Have had that happen just one time in six years and the situation made it quite clear that is was pneumonia, not some contagious respiratory illness.
Not sure why someone brought up a very old post in this thread, but I've said over and over again that I am not telling anyone what to do with their flock--a reminder here that this is my summary of my own flock management system that has worked for me for years. Do with it as you will. It works as well as you can reasonably expect it would. If you are okay with treating illness upon illness of carrier flocks, it's not my concern. That is your beeswax. It only becomes my concern when someone sells a bird who is carrying a virus or bacterial illness to another BYC member and we catch the dispute here or if I were to purchase a bird from someone else (which I do not do) and it brings disease onto my property and into my previously healthy flock.