TOPIC:

I have often heard to not use a helmet for more than 5 years. Would that also apply to a new, unused leftover helmet that is older than that? NOS.

If stored is a reasonable environment, I wouldn't be worried about 10 years, or longer.

I read in the original Hurt report that a helmet will last even longer than ten years. It’s usually the padding that that starts crumbling apart.
The ECE has a brand new standard called ECE 22.06
HJC has a new helmet called the C10 which has the 22.06 rating. It sells for about $100 bucks!

I think the material it's made of also has an impact. For example fibreglass degrades over time - I guess the questions is what level of risk are you comfortable with

I have three current helmets which I change up once they get funky and uncomfortable. It’s amazing how nice an old helmet feels when you remove the lining and hand wash in Woolite.
I never spend big bucks on helmets. I prefer to stay in the $200 dollar range but ALL of my helmets are Sharp five star safety rated helmets. Four stars won’t cut it.
My guess is, once Sharp rates the C10, it gets five stars. We’ll see. 
Most recently I bought a weird Bell Eliminator helmet for use on my big scooter. I paid $220 US. It is five star Sharp rated with ALL GREEN in the impact zones. Expensive Shoei and Arai don’t even achieve that.

As long as it hasn't been dropped or otherwise damaged there's no reason not to keep on using an existing helmet or an old NOS item.
 

As I said, the choice is yours to decide on the risk level you are comfortable with. However I think the below from Arai is interesting with regards the invisible degradation that effects the "impact absorption" properties (the cynics could say it's a sales ploy !!). Ultimately you "pays your money and takes your choice"   (you won't get past scrutineering at most motorsport events with an "out of date lid")

 

After buying my first motrcycle  I needed helmets for me and my gal. 
 So as a young man I went to KMarts and bought 2 helmets  . One Blue Metalflake for me and a Red metalflake for my girlfriend .
 Total cost was around  40 Dollars .  
 Now I was legal  but stupid. 
Next time going to buy a new  helmet  I was  better informed . 
 I had been convinced  that my head and life were worth more than  20 bucks.
So I went for the best . A Snell Foundation tested and rated Helmet.
Mostly Bell and Simpson  Helmets . Loved the Simpson darth vader look 
That's all I have purchased since. 
What is your life worth to you and your family.?
Check out Snell and other top rated helmets and there  criteria  for impact / and age  of  usefullness 
Dave

What’s on your head? It’s easy to find out if they’ve tested it.
sharp.dft.gov.uk

Street Fighter LTD wrote:

After buying my first motrcycle  I needed helmets for me and my gal. 
 So as a young man I went to KMarts and bought 2 helmets  . One Blue Metalflake for me and a Red metalflake for my girlfriend .
 Total cost was around  40 Dollars .  
 Now I was legal  but stupid. 
Next time going to buy a new  helmet  I was  better informed . 
 I had been convinced  that my head and life were worth more than  20 bucks.
So I went for the best . A Snell Foundation tested and rated Helmet.
Mostly Bell and Simpson  Helmets . Loved the Simpson darth vader look 
That's all I have purchased since. 
What is your life worth to you and your family.?
Check out Snell and other top rated helmets and there  criteria  for impact / and age  of  usefullness 
Dave


 

Even when I bought my first motorcycle a honda CB160. The next thing I bought was a Bell Star full face helmet. It cost half of what my 160 honda cost!! I was one of the first people in my town that had a full face helmet. My boyhood hero was Dan Gurney so I had to have a black Bell Star!!

I had two serious crashes wearing Bell Star helmets. I sent one back to Bell to see if it could be repaired. A few weeks later Bell called me back and told me the helmet was unrepairable. She then asked me what I had hit. I told her the back of a Brinks truck. Silence fell over the phone for a good 10 or 15 seconds. After that I told her if it wasn't for your helmet I most likely wouldn't be  talking to you now. My whole life I ALWAYS bought top of the line helmets. My head is worth it!!!!