Yes, this happens always when they are stored with their large side on the surface (cover up). This happens even faster, when other boxes are then put on top of the first box (more weight). Sadly, a lot of sellers on eBay who empty their storage had the boxes stored exactly this way. A better way is to put them with their smaller side on the surface, this delays the bending process. If you have them sitting on a shelf, use sustainers, too. I suppose the best way would be, to re-shrink them, but I haven't tried yet...

This is just my humble opinion.

Traveller wrote:Shrink wrap?  If anything, that might hasten the bending process.

Hm. The original idea was, that the box would have no more space for bending. But, remembering the squashed shrinked Dark Sun Boxes I've seen, that's probably an illusion. I guess, you're right there.

BTW, those Dark Sun boxes were really very poorly constructed. The new format (with the flip-books) was nice, but the boxes of my playing copies are all bent and squashed now ... That's very different with the Al-Qadim boxes, which were released at nearly the same time. These wre made of really hard cardboard. However, even though they were much more solid and also had shorter sides than regular boxed settings, they eventually bend when stored wrong.