Mine have...especially the pre-WWII material from
Casino de VICHY and MONACO. I find the more
contemporary material from the last 40-years has
survived quite well. There were too many different
plasticizers used after Celuloid-type plastics were
found unsafe...and too many for me to have studied them. I suggest
the more modern material currently being offered as
the safest to collect, though I do have plastic-types much older that hold up very well. I'm not a chemist, and not able to add too much more. Sorry.

JB