I think the WetFire cubes must have something volatile in them, something that allows them to burn even in water. I imagine that when the packaging is compromised, the volatile compounds evaporate or sublimate away.

I've kind of decided that as much as I like WetFire that it isn't really practical. A tinder that isn't durable and dependable isn't really all that helpful. Maybe if I lived in a wet climate the hassle of constantly rotating stock and carrying it in a hard sided container would be worth it.

HJ