Cooked food / heat and serve meal, long term packaging
The commonest (in my experience - probably variable around the world) consumer DIY approach to this is the one that uses the step that you missed - high temperature (as mentioned by @John Feltz) - namely, pressure canning at 15 PSI (250°F) - in my experience, glass canning jars with metal lids, but flexible packages are evidently consumer-available more commonly that I've seen them around the world (perhaps even here, if I was looking for them.) 

I've certainly eaten canned items stored at room temperature well older than 15 months and lived to tell the tale - indeed, I don't consider it anything to think about, other than verifying that the jar is, in fact, still sealed when time comes to use it. This may well not coincide with the most-paranoid recommendations on canned food shelf-life, but surely someone will be along to give the most-paranoid view shortly.