John; I had the older plaques in mind when I made my post.... but I would err on the side of caution with the newer style acrylic plaqes also.

As you well know John, these older plaques do deteroriate over time and eventually will disintegrate and actually crumble from the formaldahyde ingredients breaking down that were used to manufacture the older style plaques... especially when placed in plastic pouches such as album pages or large pvc holders.

My own experience is that I've had some plaques warp as a result of too many plaques being over-housed in a bulged-out 3 ring binder where I couldn't even close the covers. I just urge others to use caution when storing them. Probably stacked on edge in some sort of suitable rigid container such as a metal or wooden index card file box would be suitable for long term storage.