Thank's. They say (Manufactures) that a helmet should be replaced every five years or if dropped. Storage location & care plays a big part in the life of a helmet. The more expensive helmets damping foam exterior has a thin black coating which is under the liner. It turns white when impacted. This should be looked at after a mishap. I remove my liners a few times a year for cleaning & inspect the foam at that time.
I sold my 2016 black in gray SHOEI helmet in med on Ebay for $400 shipped last June. It was to tight & hurt my head. . Last week Deland Motorsports of Deland FL had a sale on SHOEI helmets. Retail price was $670. I paid $480 for a large flat black in white helmet. .