Storing of boxed/carded vintage action figures?

Hi people,I have a huge vintage collection of starwars and other action figures from the 70"s and early 80"s.Most of them are still in their box and carded.I have wrapped them in clear plastic sheets to give them added protection.I recently came to know that the chemical from the plastic sheets can detoriate the condition of the box and card. Is this true and are there any better way to store them? Currenty they are stored in a dark cupboard. Please help..