Honestly, Ive been reading everything on this site for over five years and I think I’ve seen one single report of foam deteriorating and sticking to chips, so it doesn’t seem to be a common occurrence. Personally I wouldnt worry about it, especially if they’re stored in a temperature controlled place. But otherwise, cardboard boxes should be fine. Or really any kind of box or case. Hell, they should be fine stacked in racks. The room where they’re being stored seems far more important that’s anything else - no extreme heat and no direct sunlight would be my only concerns.