I don't think a blanket statement regarding this is possible. At a very high level, everything degrades over time. To focus specifically on what I think you are asking, and statements I have seen as well, I think the plastics that have had this problem have used an organic plasticizer (soybean oil, etc). They can work very well short term, but depending on moisture, contaminants, etc. may turn rancid over time.
There are a ton of variables with plastic. Quality control is a full time job and the toughest part is that some issues don't manifest for over a year. Given that raw raw materials (the materials used in stabilizers, etc.) are out of your control, Exxon, Eastman, PolyOne, etc. control this, it makes it pretty tough to predict the future.
We keep samples of every batch we make. We keep an eye on them and have them if we need to address a problem in the future. This isn't unique to the bait industry. We owned a car once with a black dash. About a year after buying it the dash started chalking. This is a major auto mfg. and they had a problem with their plastic. I think all brands in the fishing industry have an issue from time to time. The good news is a lot of them can be addressed.
My biggest advice would be to not stock pile raw plastic to save a few cents. Really watch your moisture, direct sun light, fluctuating temps, contaminants, etc.
Jason
