If you have been in the tech circles in the last couple of years you will have heard about Soylent, powdered food for techies and folk who don't want the hassle making food. Sadly its not available in the UK (at least without paying shipping and import fees).
I found a couple offerings this side of the pond but none were too satisfactory, shipping delays and other faff being the main issues. Until I stumbled upon Huel. Same idea as Soylent but made in the UK, next day delivery with a reputable courier and 100% RDA of everything.
The "food" is dry powder and comes in plastic foil lined bags which are sealed from the factory. I figure they are ripe for food storage. 1 bag is 14 meals at 500 calories a go. 4 bags is a month of calories, assuming a daily intake of 2000 calories. Since they are foil lined, the use by date is a good 8-12 months but being dry powder and (presumably) relatively sterile, the shelf life is probably a good bit longer.
There will likely be a cutoff point where the powder does start to spoil so it will need rotating out. A simple way to keep track of it is to just write the delivery date on the bags I get.
I keep one bag in my bugout/travel bag and another in a pelican case which I can wheel along behind me. If I need to hightail it out, I have at least 2 weeks of food. These 2 bags are the first to be rotated when I get a new delivery which ensures I have the longest life for any bugging out. Old bags get slotted into storage by date order and consumed in time.
I use Taskwarrior to remind me to order more Huel on a monthly basis:
$ t add project:foostorage recur:monthly wait:due-2days Buy 5 bags of Huel
I get my Huel deliveries in 4 or 5 bags a go, my one or two meals a day means I only consume about 3 bags worth a month. If I get 4 or 5 bags every month, then over the course of a year, I can build up several months of stored food. Assuming I can procure potable water, I can basically live for an extended time without having to procure sustenance of any significant value.
Now, I'm not one of those people who are on 100% Huel, I like my real food too much to do that, but I usually have one "meal" for breakfast and depending on what is going on with work, another one or two that day, with a real meal at some point during the day.