Since I deal mainly in Pythons, I've got it easier than folks dealing with different species of snake. Still I quarantine all new snakes for a minimum of 30 days. It's just the safe thing to do. Sounds like you're doing what you need to do for your herps.
You can pre- treat for mites, spray down the new cage & let dry before the new snake goes in. Mites can come from infested natural bedding, drift wood (a big culprit) things like that. So avoiding those type items are helpful.