Yes, I know, that's the conventional wisdom. But even after seeing it written on the internet over and over, I'm not convinced it's true.
If I was a helmet manufacturer, it would be pretty easy to just say "yeah, the eps liner will start to degrade after 5 years, so you better just buy another one". Oh, and how convenient that the deterioration is not noticeable or visually verifiable.
Has a reliable, independent, 3rd party ever actually tested that? I mean like take a new helmet off the shelf, do the SNELL drop tests (or whatever), have someone wear the helmet in the real world for 10 years, then test it again?