Hang on. You say you're protecting against "disruption of food delivery", but then you're talking about 2 years' worth of stocks? Those two statements can't both be correct, unless by "disruption of food delivery" you're talking about a complete breakdown of all national forms of transport for that long. But the only thing which could cause that would be an attack from some WMD - nuclear, chemical or biological - such that the country's transport infrastructure was irreparably damaged and all senior people (political and military) who could do something about it were dead.

It's certainly possible to plan for a post-apocalyptic scenario. But that opens the question of how likely you consider the apocalypse to be. Most apocalypse predictors are clinically paranoid. You might not be, but the odds are on the other side... :-/

Graham.