Based on your reading is the expiry date of ceramic mostly (or entirely) bullshit? And recognize at least in my case this stuff is sitting on a dark shelf or something so I'm not out on tour for five years knocking it around.
That sounds correct.
Sitting in your basement really doesn't cause any wear and tear like bouncing around in a hot and cold truck of a vehicle will cause.
I think the 5years is more for warranty and certification than anything. I think what the manufacturer says is they can't certify them for longer than 5 years. It could just be an NIJ rule. I don't know.