I bought mine from Chevy Duty (now Classicparts) back in 1998 and installed it on a new windshield. That glass was smashed in 2002. The gasket was cleaned up and reused, and it still looks like new. My truck has always been garage kept so that may be part of the reason it remains in such good condition. If I ever need another one I’ll no doubt buy from the same supplier.
Here’s what it looked like in 2002:
And here’s what the gasket looked like a year ago. It looks exactly the same today. There isn't any detectable deterioration:
