We keep new additions in a separate room from our main collection for at least 2, often 3 months. We maintain them on paper towel bedding to observe feces and check for mites. They are treated for mites if I have any doubts about the source or if they came through a reptile show. We look after them after we have dealt with the main collection - never feed, clean or handle the new guys and then go into the main collection rooms without washing hands. We don't do routine fecals on new additions now, but know that some people do. If we observe or have to treat any problems, the time in isolation increases.
hope this helps,
mary v.