>>28576454
>>28576458
>>28576463
>>28576488
As usual, it's the *bicycle* helmet community that has come through with the engineering studies to prove that helmets don't expire. Bicycle helmets are made the same way with the same materials as motorcycle helmets, just to different standards.
The explain-it-like-you're-five-and-from /DBT/ is here:
https://helmets.org/up1505a.htm