Keeping 8L bottles of water around is an exercise in of itself, they’re easy to forget and bottled water doesn’t last terribly long so you meed to remember to cycle it.
(120 days for normal filtered water with heavy agitation, 2 years for distilled sealed water).
If I forget, and there's then a situation where it's the only thing I have to drink, I won't worry about it being past the date.
For water, could get a water cooler. Keep a few 5 gal jugs around, and just use it for some drinking water. By periodically using it, you’re able to rotate through jugs.
For food, plan canned food supplies around what you normally eat.
For example, I like soup in the winter and fall, so I’m always cycling through it every year.
Another couple of days are from me eating various kinds of instant noodles. I always have a dozen or so at hand.
I buy bulk oatmeal for breakfast as part of my normal breakfast routine. That’s several days of food in a pinch.
I go camping several times a year so the freeze-dried foods are worthwhile keeping stocked up, and I just bring a few when I go out.
If you use your pantry as part of your supply planning, the hardest part isn’t stocking up, it’s tracking nutrients.
If you know you need a can of tuna for tuna salad, buy two. If you only have one in your pantry, get a second one the next time you go shopping. Just having a backup bottle of ketchup is amazing, because you always notice you've got a mostly empty bottle of it when the pasta is already cooked an everyone is hungry.
Plant proteins are good for storage, beans, chickpeas and even soy in different forms store well and are easy to use in day to day cooking. You can only take so much canned tuna and other canned meats are either crazy expensive or just plain gross.
Just remember to ONLY stock up on food you actually use. Don't buy a massive box of dried camping food unless you go camping and actually eat it. It's not exactly gourmet even when it's fresh - even less so when it expired in 2015. Ask me how I know :D
I have one of those for every member of the family (including pets) and a calendar alarm a month before they go "bad". Then we either use them for boiling pasta/potatoes or watering the flowers and get new ones.
We've had to tap into them ... twice in a decade I think? Once when a neighbour did some DIY plumbing and the water was shut down for 12 hours while actual professionals fixed their oopsie and once when the municipal water treatment plant fucked up and the water was tainted for a bit.
We have 22,000 litres of water stored, with pumps and filters. And we are on mains water too so it’s never used.
We also have 6,000 litres of water stored for fire fighting.
As do many other houses on our street and local area.
Then there is the solar and storage batteries…
We could go for a good while and we live in a metropolitan area!
Rural Australians could probably survive for longer as isolation is their life anyway LOL ;-)
Bottled water in France at least has a 1-year expiration date. I have drunk water well past this date without noticing any particular taste.
In case of disaster water necessities could be covered by cooling hot water from the water heater.