>>47408137It's still possible to get edgewear and scratches through the wrapper, but the only thing directly hamrful about them is polymer leakage from the cheap cellophane they use. There's really nothing you can do to prevent it from happening altogether, so it should be opened /eventually/, but if stored in a cool and dry environment, occasionally taken out for a day or two to "breathe," it can last for 50 years or so.
If you open it and the card is sticky, that's leakage. I don't really know how you'd go about cleaning it off at that point as the usual solution is warm water and soap.
