Yeah, I had some that were something more than 20 years old. I opened one, tried to light it with a match, and it didn't, so I threw out the lot.

I'm no expert about it's chemical toxicity, but I've heard enough that I replaced the stock with Esbit tablets, which at least claim to be non-toxic. As a side benefit, they're also useful for powering a couple of model Stirling engines from time to time, just to illustrate the principles....