I bought a couple of Strike Forces years ago, close to 15, I think. I also purchased some extra tinder cubes with them when I bought them. I just checked and they all are intact. This was when the StrikeForce was marketed by Gerber.
I also have several packs of Esbit fuel, I have not noticed any deterioration in performance in any of those, but I can attest to the fact there is a very distinct odor when I open the airtight container I store them in.
You all have me thinking about just sticking to Trioxane and petroleum-jellied cotton balls. I will test my stores as well and get back with you, also.