Rubber legs

I have several packages of Rainy's brand round rubber leg material that are behaving oddly. My large packages, stored in their original zip lock bags for over a year, are in great condition. The smaller assortments that I have placed in with my assortment of"active" materials (a large Plano tackle box) and are just lying loose have completely dried out and are crumbling apart.
Has anyone else had any similar experience? How can it be explained?

It's exactly what you said: they dried out. The plasticizers evaporate over time. Stored in a small air tight container (like the original packaging) there's not enough air for them to evaporate into; in the the less than air tight tackle box, there's plenty.

They'll also dry out on finished flies.

I think the "sili legs" stay good for longer?

I've experienced this issue with white rubber legs, not any other color. All same brand.

Thanks guys. I sort of assumed that, but I'm amazed that it is so much more pronounced with that particular brand and not so with others. I have really old stuff (10 years plus) that is as good as new that has been in the open all the time.
The particular variety of rubber, silicone or other must be the real governing factor. Now I will just have to be "brand specific".

How far are you from the ocean? I know that here on Kauai, with the salt air, materials deteriorate more quickly than in an inland location.

Where did my reply about using UV cement disappear to ?

Sorry, I misaddressed this reply And I don't know how to cancel it.