Roood, definitely keep the gunmetal grey one sealed, I'm 100% sure you will find one to buy it from you at a really good price.
Tell your GF that in 10 years, there might be no spare parts available for the JetBeam and the Olight, we'll see, but for the Surefires it's not gonna be a problem. First, what should break on a G2 C2, or 6P? With the original twisty tailcaps there's really nothing on those lights that can break except the lens and the o-rings. And secondly there's the surefire lifetime warranty. And last but not least, there are so many of these lights around. Availability of spare parts depends on the demand. If only ten guys own a light nobody will give them spare parts, probably not even the manufacturer. But there are literally tens of thousands of these lights around.