I quarantine all of my snakes for a month if I know that they're coming from a reputable breeder. If the source is from a new breeder, or pet store, or if I know the balls were raised in house with boas, it's three months, to try to wait out BIC if it's present. Usually a month is good though, for those standard illnesses. Make sure to wash your hands after handling the new snake! It's easy to forget if they're in another room and you want to check on the first one.