That’s only 10 days at 2,500/day for an adult male.
I suppose you could buy a bucket every year and retire them once they run out, then you’ve always got 250 days on hand.
Just to clarify, I don’t think I’d have enough in the house even for a week at the moment.
As to why Mormons tend to be so into it, I have a theory. The Mormons started out very poor (generally speaking), and repeately ended up leaving their homes and starting anew, including at one point in the barren and remote mountain west (where their headquarters are today). Having stores of food and other supplies were literally a matter of life and death and survival. I think that same spirit is still active among them.
What's interesting to me is that Judaism doesn't have any kind of similar requirement. There you also have a history (or at least a stereotype) of having to pick and up and move in response to religious persecution. I wonder if it's because in reality the gaps in time between periods of stability and persecution were often quite large? I don't think Jews have historically seen themselves as a wandering people as much as outsiders have seen them that way.
Mormons, meanwhile, had to move from place to place in quick succession over less than half a decade. It's another reason why LDS Church feels like the ultimate American religion: prepping is baked directly into the religious practice.
No need to theorize, the rapture plays a big role in their canon, and is proselytized heavily.
Some guy was oh-so-excited to show me the back of his truck, and how he had set it up to live there if he needed to. He had a whole solar setup.
(And, even though I'm not a prepper, I bought one of these buckets, and iodine pills, when war broke out in Ukraine.)
So perhaps the optimal strategy would be a combination of the two (likely with other options as well such as a supply of dried fruit to provide vitamin C).
This is the basis of how my family does things these days.
Post-COVID, we keep about 200# of rice and another 200# of dried beans on hand. We also have corresponding dry seasonings and such on hand. It's cheap, and stores well.
We eat quite a bit of both, but the above stay untouched. Once a year we donate it all to our local food pantry (i.e., "soup kitchen") and replace it. We know that it's useful for them because we work a shift at least once a month; we're not just pawning it off blindly. The donation is a tax write-off, and replacing the whole thing is less than $500.
Before COVID, we did the same but with small quantities. Our experience there showed us that it was in fact valuable to have food and essentials on hand just in case, and it felt justified to spend a bit more money on it in order to have more.
If you want to go down that rabbit hole, start with studying Katrina. Has almost every variation played out within one extensively documented event. Hunker vs leave, severe acute damage (MS) vs persistent 'lessor' flooding (NOLA), figuring out how long you need to evac, and when evac turns into short/medium term relocation or even permanent move.
Yea it's local and not Armageddon, but it provides the framework for how to think about these things, and how relying on faulty assumptions gets you in trouble.
But the real answer to your Q is that you'll start by prepping for 10-day events, then 100-day events, then maybe 250-day events, and you'll start to be able to fill in the gaps of your knowledge yourself. No matter what the risks.
Along the lines of: What good is 250 days of food without X? Where x might be water, fuel, meds, or 'lessor' needs like internet, work/job, social events, etc.
Or what good is 250 days of food if I have to abandon 210 days of that supply to evac?
Those are the types of questions that people answer differently, and you won't start filling in the gaps for yourself until you start small and build from there.