Originally Posted by
Lazyass
The 3-5 year rule is because of UV rays breaking down the foam and glue. That's the reasoning, anyway. Same in the motorcycle world. Those helmet manufacturers won't warranty a helmet past 5 years and stop selling replacement parts (padding, visors) for the old models. My current helmet was bought 5 years ago. I ordered a new Giro a few days ago simply because it was 50% off and I was ready for something new.
UV affects a thin layer on the surface, but not with the plastic cover on it. I've had the glue on the conver break down after a few years, but 10 minutes with some Gorilla Glue* fixed that up.
Mine get ratty after 4-5 years and when it feels too embarrassing to wear it in public I replace them.
*might have been Elmer's. You do have to be careful which glue you use.