Hmm what about microfiche?
If you care about long-term archiving, don't store the microfiche in the
boxes that have foam padding. The padding crumbles to dust or goo (as I'm
sure most of us have seen inside old minicomputers and such). That wouldn't
be so bad in and of itself, except that the foam residue actually
*reacts* with the microfiche, rendering it unreadable. :-(