Originally Posted by JohnJ80

Helmet manufacturers recommend replacement after a time period due to material aging, UV, and experience with their products from field evaluations.

Originally Posted by gugie

I agree with everything you wrote except the first sentence. Based on the study, it would seem that material aging and UV probably are not a factor They didn't control for UV exposure, but the large data set would suggest that they would have captured at least some "UV damaged" helmets. Is there any data from manufacturers to support the recommended replacement interval?

I think that helmet manufacturers recommend replacement to sell more helmets, using safety as an issue.

All of this points out that time is not a factor. So why replace a helmet after a certain time period at all?