Again, this is 'in my experience.' The only wads where I've encountered rot & brittleness have been older Winchester AA wads that were still in their original plastic bags. My thought is that there is an incompatibility between the two plastics that is causing this degrading but like one of our former members who has left the range used to say, "I could be wrong.' I say that because I've used even older Winchester AA wads that were packaged in cardboard boxes when they were first made available for sale that exhibited no sign of degrading and had remained very pliable... and therefor don't consider that there would be anything to worry about in an older factory loaded round, where the wad is concerned. Any Winchester AA wads in plastic packaging I deem suspect and 'test' for pliability by folding a petal back against several of the wad's sides and seeing if it returns to its original place.
I did experience some issues at one time with another short-lived brand of aftermarket 12 ga wad that was made w/an unsuitable plastic and also was blowing through the top of the over-powder portion of the wad on firing and the seller of those wads made me whole, when I pointed out the flaws & reason for my dissatisfaction to him. AFAIK, none of those wads are to be found anywhere... at this late date.
I've also used numbers of quite old plastic Remington Power Piston™, Federal 12 C-1 & 2 wads, 28 ga Federal Pushin Cushion™, 20 ga Wind Jammers and even Herter's 12 ga 'Chalice' and Lage Uni-wads that were all as pliable as the day they were made, even though many were 30+ years old. No degradation in the plastics used being noted.
