I understand the concern. The helmet looks like it was stored in its box for most of those 21 years. It's like everything motorcycle related in that it's a roll of the dice. I've known people to die in full leathers in city traffic and then seen drunks flung off of harleys at 100+ mph with no gear and live to tell the tale.
The Arai by all rights looks better built than any present day helmet under 200 dollars in terms of safety tech and quality. I know that styrofoam can degrade and I'm sure we've all seen rotting styrofoam buoys in water and sunlight that eventually turn to white dust. But this looks and feels solid. But like I already admitted, I haven't been wearing a DOT rated helmet for the past 10 years, so it's a step up from what I have. Also having the safest helmet made that doesn't fit you right is more dangerous. I need something that I'm not fiddling with constantly while riding. These helmets are pretty straightforward and fit my head properly.
There's not much magic involved in modern helmet design. It's plastic, fiberglass, or carbon laid over top of styrofoam and some padding for comfort. The companies we all know and love PROBABLY try to make it such that the outer shell works as a structural unit to save your brain. I have ZERO faith in the cheap companies like HJC, Gmax, Fulmer, etc.... who seem to just be rushing to create next year's 100 dollar eye candy at the motorcycle shops.
By the same logic that helmets expire, bikes should also expire though. A 5 year old bike is typically less safe than a new one in terms of wear and tear. Most people don't maintain their bikes to the T and safety items like the brakes and tires put people at risks of a wreck. Coats should expire since rain and UV probably damages the materials, and the list goes on and on. Helmets are like motor oil. Most people have pretty set and strong opinions about them just based on how our culture has evolved. There's no helmet law here, so it's rare to even see anyone wearing one. I'm not saying it makes any sense, but that's just how it goes. It's also less populated here, so not that many people die per year on bikes as compared to other parts of the nation where traffic is a lot heavier.
I trust this Arai over any new 3/4 or 1/2 helmet and would go so far as to say almost any modular helmet. But that's just me gambling with my own head trauma risks. I've always thought of helmets in the terms that you get one bounce to protect your brain. Then the full face chin bar is there for when you slide. I've had the good fortune to not need to find out in my past 25 years of riding. Soon we're all going to be owners of a 75 horsepower motorcycle that could kill us regardless of what we're wearing, in an instant IF the cards are not in our favor that moment.
The owners manual for the Arai is interesting... It has anime drawings before anime was even a thing in the USA:
I don't expect anyone to think I'm the beacon of safety since I'm not. I also am very much in favor of nobody copying my behavior, or do so at their own risk. I am also not looking to argue back and forth about it since I doubt anyone's opinion would change
I just got this jacket for summer time. It's basically a skin tight hockey jersey with armor. But it has chest armor which I felt was important given the amount of people who have nice jackets but no armor in them. Then again, if I slide, that mesh is going to shred and all of the armor is going to fly out of it. But it's just one of the calculated buying decisions I've made.