Distributor question

Ok... Related questions.
What would the "shelf life" of old NOS plastic ones be? Would the plastic either get more brittle or somehow "soften up" from having sat on a shelf somewhere? Whether factory NOS or aftermarket NOS?
As we all know these gears aren't as readily available anymore, (there used to be a couple of them on every "lazy Susan" style parts store display back in the day/ but some parts stores can't seem to even order one anymore)
Does anyone even make them anymore?
We all know how long it's been since these engines were common on the roads. Not the same as "current models" but "commonly seen running around".

In my case I'm running an original '74 cam that I sent in to Oregon cams to be reground. Not a more recent aftermarket cam that seemed more likely to have cam gear deterioration issues.

That said/ that 79 truck I had, I replaced the engine back around 1988 because the cam gear shredded. And i'd had that truck a couple of years by then and I knew the guy I got it from, I know that he was never inside that engine. It was pretty low mile when he got it, it started eating distributor gears a bit before the cam gear shredded. If you'd have cut the cam off either side of the distributor and oil pump drive gear it would have looked like a "D" cross section, with all teeth shredded off one side, far from round.
At the end for that engine I sat in a farm field access, on the side of the road and replaced that plastic gear 3x before I realized what was wrong.
In that 3rd time of replacement the that afternoon when I went to drop the distributor back in the "flat side" of the gear was facing up where I could see it.... As far as I know that was the original cam to that motor.