StyrbjornSterki said:
The answer is: every eight years. Or never. Maybe.
Bicycle Helmet Safety Institute:
When Should I Replace My Helmet?
Netserk said:
Nets - you crack me up!
The BHSI article covers the ground extremely well. I recall from somewhere a Bell Biker that was many years old and out of date being put under the ANSI standard test - and passing with flying colors.
Salt doesn't degrade the foam or plastic. Sunlight does, but it takes a LOT - so if you've left it sit in the car back window for the past few years - probably time to replace. Normal ride time sunlight is not enough - unless you've been circumnavigating the globe daily for the past 5 or so years.
Most helmets today, I think, use glue to hold in the retention straps at some point. This glue can degrade and come apart. I've got an approx 10 year old mid-range model in which the stabilizing back-of-the-head strap has come out like this. The helmet would actually still offer its protection - as the primary 3-point retention straps remain intact - and they are the real nuts and bolts of the protection paradigm. The stabilizer straps are "nice-to-have" I think.
Replacement fitting pads can get hard to find - I've made do with various substitutes. And they do get skanky!
The only other reason I've ever changed helmets has been style. The Bell Pro looked cooler than the Biker. The microshell pointy helmets then looked even cooler yet - with color schemes and everything!
But I've never been a real fan of the pointiness - so these new Air Attacks are looking interesting. Wasn't there a similar model from Kask that Cav wore last year?