

Three days is the (generously calculated) time until civil defence will have soup kitchens up and running, and at least over here they stock three months worth of lentil stew, pea stew, and bread and more than enough diesel to keep logistics, kitchens and crucial infrastructure such as water pumps running. Heating, push come to shove, would be supplied at the gymnasium of your local school or suchlike. Recommendation is to have 7-10 days worth of stock.
But yes I’d recommend against (completely) relying on stocks that need preparation because electricity and water might fail. Canned soups and stews are good and don’t forget canned peaches or such so you can have dessert. Woodgas burners are cheap camping supplies and you’re bound to be able to find some sticks somewhere so with some water reserve you even can have your morning coffee.
My prof called K&R C “Knall und Rauch C”, “bang and smoke C”. Also: C lattice fence.