Although our MH has never been left standing for more than 2 months we take nothing out and have no heating or dehumidifier. Never had a problem in over 4 years. Just drain down and move slightly every two weeks.
As ScotJimland says, warm air holds moisture so you would also need a dehumidifier to remove the moisture, on the other hand - for a dehumidifier to work properly you need heat.
As for the fridge - we just leave it open when not in use.
Jean
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