I'm sorely tempted to start a gofundme, have anyone retiring a 'good' helmet send it to me, and pay for a couple labs to do all the same testing they do on new helmets as a comparison.
I typically replace my helmets every 5-7 years.Mine are stored inside (at the very least in a garage, and it doesn't get that hot or cold here) and not left in the sun. If I drop it or do something that I know might have damage the EPS inside, I will replace it, but I really don't know that a good modern helmet ages out these days.
I'd like to really know, but I'm going out of pocket for it. :/
No sooner did I post this, than I discovered
this post.
So there you go.