>>9226402it's not rubber.
It's likely silicone or some other highly flexible material that's related to silicone.
Silicone is one of the best plastics, because it takes nearly forever to break down. This is why it's used for shit like baking and as most people know, heat is a way to make plastic degrades fast.
The way silicone degrades, it will likely turn hard over 50-500 years and then start breaking, so it'll last you a lifetime before it affects its poseability.