"Most don't crumble or go brittle. Correction most don't crumble or go brittle before we do. Entropy.
Thanks David, this is one of the most useful and practical entries that I have seen for a while. The message I take away from this is that, as with old soldiers fading away, old plastic soldiers crumble away - eventually. It's a matter of fact and a phenomenon of the material they are made from.
I agree that it is frustrating - to say the least - when a recently bought set starts to crumble, and I agree that we need a view from HaT on this. Clearly, plastic quality and composition will vary, and also will the conditions that figures exist in. Mine tend to spend most of their time in airtight food containers in a dark, stable environment, and I still have 1970s Airfix plastics which are OK. I am a little concerned over my 30mm plastic SYW figures, which are of a different plastic and do look set to deteriorate. However, in general let's remember that nothing lasts forever, and enjoy our armies while we - and they - are still young-ish.