old brittle plastic corner keys

Good question. I'm not sure if the newer corners we carry use a better quality plastic than the old hardware. I know that manufacturers always try to improve on their products, however with this kind of thing there is only so much you can do. You have to keep in mind that the big culprit is the sun itself, which damages most hardware installed in a window. Insulated glass, vinyl frames, etc. It'll even give you a bad sunburn! No matter the quality of the plastic, it will eventually succumb to the ultra violet rays. The more exposed a window is, the quicker this will happen.