I can go along with the interior foam degrading over time. I think five years should be a standard time frame. As for the shell of the helmet, if it is fiberglass or a composite, I find it hard to believe that it will degrade over time and/or getting chemicals on it. If that were the case, then there are a bunch of fiberglass and Kevlar boats out there that are in danger of breaking up. I have used everything from Acetone to MEK to clean fiberglass and it does not affect strength. I worked on a race boat (first Kevlar Cigarette, it was a 38 Top Gun) that took a hell of a beating and showed no signs of delamination or crazing. I honestly think the "dropped lid scenario" is to cover somebodies ass, or maybe it's good for PolyCarbonate shells, but I really doubt it will really affect a Fiberglass/Kevlar/Carbon Matrix. Not saying I would not replace my lid if it drops, but I honestly think we are not getting the facts in regards to composites and damage of todays helmets. To say it again, just to be safe, I would replace a dropped or crash tested helmet, but I would really like to see an independent test of what a drop or scratch really does to a helmet. JMHO so let the flames fly (BTW - I have worked in the Marine Industry for 30 years and have worked with Fiberglass, Carbon Fiber and Kelvar as well as Epoxies and other Resins)