I like to keep mine quarantined for at least 2 months.Quaranting new birds for at least 6 weeks will give you a good idea if the new birds are infected/infested with something, then treat or cull accordingly. Keep in mind that respiratory diseases have different incubation times...that's why it's recommended 6 weeks quarantine. There are a few diseases that have longer incubation times, it's always a risk. Usually though, the stress of quarantine will bring out the worst of an infected bird in a couple of weeks. You'll want to practice biosecurity too. Diseases can be transmitted on clothing, shoes, hands, sometimes airborne etc...Keeping newly quarantined birds the farthest away from a healthy flock is best.
Sorry for hijacking your thread Kat!