imported post
Here's my story. I had a helmet for 27 years at one time! Bought it new with the bike, and still had it when I sold the bike 27 years later! I thought they lasted for ever - as long as you had a hard shell on your head, you were protected. Was I ever wrong (and lucky I never needed the protection!)
When I was at the dealer when I sold my bike, I put the helmet down on the service counter, and the service rep noticed the date on it - he nearly passed out!
That led me to buy a new helmet, even though the old one looked pristine, just like my 27 year old Honda, which looked like it had just come out of the show room! You see, I didn't ride much in those days, and the bike only had 5,000 miles on it, so I figured the helmet was still like new as well!
Anyway, after a lot of research, I learnt that a helmet protects your head by absorbing the energy of an impact and not passing that energy on to your head. And the thing in the helmet that absorbs most of the energy is the thick foam lining, not the plastic outer shell which I thought was the protector.
As time goes by, the foam - no matter how well it is treated - loses it's resiliency, goes hard, and is thereafter unable to absorb the energy of an impact - ergo, it should be tossed!
Most of the organizations that test the helmets (like Snell) suggest that by 8 years it is no longer much good for protection. Do you want to wait right to the end, or replace it before it can't protect you, that is the question.
I personally think that it would be prudent to replace a helmet every 6 years or so before it is unable to protect you.
Interestingly enough, the research data showed that the more expensive helmets did not necessarily give better protection, so do your homework before you buy if this factor is important to you.
Ride safe and protect your head as well as you can, it is the most valuable part of your body, and also probably the most vulnerable in an accident!