Wow, never even considered this over the years, just always got tired of my lids and replaced them....
Found on SMF.org site: (and it mirrors just about every helmet makers suggestions)
<div class="iF-Passage"><div class="QUOTEHEAD">Quote:</div><div class="QUOTE clearfix"><span class="quoteBegin"> </span>
Replacing Your Helmet
by: Ed Hunter
How often should you replace your helmet?
You know that smelly old thing that you have been wearing for years. Just got comfortable, didn't it.
First some background: I work for the SNELL MEMORIAL FOUNDATION as a Lab Technician testing helmets. This means I have some knowledge about helmet testing and standards, plus access to helmet test equipment.
For years now when people find out where I work, one of the first questions asked is "how long do helmets last"? In an attempt to answer the question, I asked my riding friends to give me their old helmets for testing. The procedure used was to identify each helmet's original test standard because it would be unreasonable to expect a helmet certified in 1970 to withstand the impacts required by the 2000 standard. For SNELL certified helmets this was easy. Each certified helmet contains a sticker indicating the standard. For non certified helmets, I used the standard that was in effect at the time of manufacture. Although there are other helmet standards in the world, I tested all helmets to the applicable SNELL standard. The helmets were rigorously tested, but the exercise was informal because there was no control group of helmets and no attempt to ascertain the treatment each helmet had received over the years. Since 1996, I tested 26 different helmets representing 8 different manufacturers. The oldest helmet was certified to the SNELL 1962 standard and the newest had a 1990 SNELL sticker.
What!
You want to know the results of all this testing?
Over half of the helmets were able to pass the test prescribed by the original standard.
No, I will not identify those that passed or failed.
What does it all mean? I think it means that the recommendation of many manufacturers to replace your helmet every five years is as good as any. I believe helmets left in the box, on the shelf will last a long, long time. Of course, they won't provide you much protection while you're out riding and they're setting on the shelf. There are at least three things to keep in mind when considering whether to purchase a new helmet; one, how has the helmet been treated; two, how far have the standards advanced; and three, how does it smell. [/quote]
I also found info that said 3 years or (and this would relate to previous threads about dropping your lid) any helmet that has been dropped from more than "knee" height. They cited UV damage, along with liner, adhesive degradation over time.
Without being overly paranoid, sounds to me like 5 years (without any drops) should be a good number..
I personally would not shy away from a longer period on my buckets as they get alternated and no longer see the abuse of the southwest sun/heat..
Now I have to go look at production dates in my lids.....
