They can stay down for 3 months, even 4 months depending on conditions(ie as long as you can keep the cage cool enough). Just check periodically to make sure they have good body weight. Make sure the cage is dry and they always have fresh water available; a moist hide is ok too.

Things to watch out for are pacing(too warm), wheezing or bubbles and/or mouthrot. If any of these occur you have to bring them up and treat accordingly.
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