Your question got me curious, so I attempted to call (at random) a selection of Insurance Agencies in my area, to see if I could find a concensus.
Turns out, MOST of them were CLOSED today (a Saturday). Then the one Agent that I DID actually speak to, at one particular Agency, (Don't recall their name) had a ton more to sell me (he tried) than the answer to the question I asked him.
My Question: Does Insurance typically cover helmet replacement?
Answer: (whittled down) "Yes, in accidents; pro-rated" and "Not worth it, to insure it, up front, for its own value."
Another phone conversation I had, this time with A GEICO Agent:
Me: "Do you know if Helmets are Insurable?"
Agent: "Yes, they are considered an Accessory, and there are different values applied to them, depending on the State you live in. In YOUR case (Connecticut) there is a $400.00 replacement value. Some States have a $500.00 replacement value in their GEICO Policies."
I understand the depreciation of something that accumulates mileage like the bike, but how do they calculate depreciation on a helmet? Approximate hours of use? If I were to spend less than $100 on a helmet (I do) I wouldn't really expect to get anything, but if it was $500 or more I might.