I am not a fan of quarantining as the “be all solution” for introducing new birds. While there are a few things 30 or even 60 day quarantine may catch, there are many it will miss. I think quarantining gives people a false sense of security. If it is possible, testing is better. There are several diseases, IC to name one, whereas the chickens that survive will be carriers for life. There may be or not be times that symptoms will reappear, like stress, other ailments, etc…, but this may be months or years away. Regardless, the carriers will give the flock IC.