Too bad I disposed of my old helmet. We could have taken it to the test. I bought a new helmet 2 years ago. This may surprise you: not in the package, not in the booklet that came with it, not in the helmet itself is there any warning about aging by UV-light. I read Dutch, German, English and French motormagazines. Although - long ago - some have echoed what the industry then wanted you to believe, since 1979 they have not produced one article - not one - that has shown, with pictures, the dangers of aging by UV-light, and - believe me - they have published on any aspect of motorcycling you can think of. Ofcourse, everything ages by UV-light, but it will not deteriorate your helmet before the lining is long, long gone.
Delta - go and read the technical journals there's tons of evidence in decent scientific publications supporting this. My Shoei is falling apart to the touch after nine years or did you not read that bit? And don't think that the law is any measure of this either - especially not in the Netherlands, hell you've only just passed a law to stop bestiality!
Listen to your countryman, Rob, above. He's a sensible and informed chap worthyof consideration...
Oh and here's a quote from the Arai website...
No matter how good it may look, or how well you take care of it, age still takes its toll. Even with minimal use, a helmet is affected by things like the acids and oils in sweat, haircare products, pollution, exposure to UV rays, etc. At about the five-year mark, helmet interiors begin to show wear and/or deterioration, which should serve as an alert to its overall condition. The helmet's fit may begin to feel a little "loose", not as snug as it once did. This unseen aging and deterioration of the EPS liner and fiberglass shell can affect the helmet's ability to perform in an impact as it was originally designed.
The 5 year rule should be taken from the date of manufacture which is stamped on the inside of a new helmet, or in the caes of an arai on the helmet strap, and not from the date you bought it as retailers buy in bulk they may have had the helmet a year or so before you buy it, just check when your buying it...
And one from HJC...
It is important that if a rider's model of hjc motorcycle helmets gets a crack they need to replace it. A helmet's life span is about 3 to 5 years based upon usage amount. As the helmet ages it is damaged by UV rays among other things. Remember that a helmet only protects you through one crash. In that one crash it will probably get damaged enough to need replacing.