I dunno, what I've always heard is that the polysterene liner itself isn't guaranteed to behave the same, i.e. crush at the appropriate rate, of you were to have a crash with an older helmet, as that liner ages and becomes more brittle. That crushing is what decelerates your head in as safe a manner as possible, and in turn helps protect against brain injury. The pics you loaded do show a helmet in damn good condition, and I'm not sure I'd immediately toss it either, if everything continues to feel supple and does not feel or appear damaged in any way from sun or any other long-term exposure. There are no laws on the books about when a helmet is no longer "legal", DOT certification doesn't expire at 60 months, and nobody's going to get in any trouble for using an old helmet. But it's unlikely to me that it will perform exactly as well as a new one would; and it's how much you believe that difference to be, a tiny inconsequential difference or a larger more significant difference. Up to you.
