Guess it depends on what sort of disaster you are planning for. If you live near the coast where you might have a hurricane is probably a different sort of plan from someone in the midwest where there might be a tornado. If you live in a remote area, seems the issue is more about how far away the stores are and what happens during a power failure. With an approaching hurricane you are more likely to have to evacuate and then all of those items you are stockpiling won't do you much good if you can't fit them in your car (30 gallons of water/person would take up a LOT of space). Do you periodically rotate those stored items since most likely have a shelf life? Seems like you will end up throwing a lot of things in the trash if the expected disaster never occurs.
yes on rotating so no food items are wasted. we have a whole house generator and a 1000 gallon tank so we are good for a decent period w/o power-learned during a prolonged outage of over a week one year that it outlasted the supermarkets in our region which had to toss vast amounts from their fridges and freezers.
i don't intentionaly plan to have 9 months to a years worth on hand (i would be ok with 90 days) but i avail myself of sales and end up with larger amounts at lower prices and if there were no ongoing shopping available to us i suspect our eating habits would change and we would make it last longer (our habits changed during the pandemic, some old habits have re-surfaced while others have not).