Dr. Scott Stahl, regarded as the leading reptile vet in the country, if not the world, recommends no SHORTER than a 30 day treatment and sometimes longer. Just because the symptoms are gone, doesn't mean that the illness is gone.
I've listened to his episode on Reptile Radio at least 5 times now, and I think it's one of the best shows they've done.
He specifically addresses respiratory infections and my veterinarian has listened to the episode in order to further his own education on the treatment of snakes and RI's.
http://www.blogtalkradio.com/reptile...ile-Veterinary