In terms of RIs being passed to snake to snake when being in close quarters I can say this has NOT been the case with me and my snakes. I received a big female over a year ago that came to me with an RI, and no others in that QT space got an RI from her (she cleared up and is in with the established collection now). I recently got two snakes from an expo (same vendor) who came down with mild RIs and no others in the QT have an RI now and I doubt they'll come down with one: we've been checking for signs in between feedings. Never dealt with mites, all new additions have their tubs pretreated with PAM before they even arrive.

I QT mainly for general sicknesses; IBD isn't as big as a concern to me as it's not as common as other illnesses. I QT in a separate room from the established guys.