I'd expect a couple years at least. A quick Google gives common wisdom that you still want anti-weevil measures (bay leaves in the bag, the aforementioned diatomaceous earth) with that method.
My point with that part was just that you have to do the vacuum sealing (unless you're buying a product with all this taken care of, which I'd assume is expensive) and such, at least, which means more equipment and material than simply buying sealed (but not vacuum sealed) bags at the store and putting them on a shelf. Getting grains ready for long-term storage means more than just keeping mice and bugs and water out—you've gotta worry about oxygen, and about insect eggs already present in the grain, too. Just stuff one might not think of if one were to make the wrong assumptions.
[EDIT] Incidentally, trying to store all one's calories, at least more than enough for a week or two, might not be the right idea anyway, short of a truly horrible catastrophe like nuclear war—my great-grandparents and grandparents, who lived through the depression and World War II, respectively, didn't seem to be all that in to storing lots of grain. What they were into, big time, was canning vegetables, and gardening (to grow stuff to put in the cans). Man, were they ever into canning vegetables. I'd guess that's the result of some hard lessons about how to make it through hard times—plus, just, times before modern shipping and refrigeration when food availability dropped a whole bunch in Winter.
Maybe the misunderstanding stems from a geographic difference. The rice I buy seems to come in an under a co2-atmosphere vacuum sealed bag that costs around $2 (or less on sale) per kg.
> What they were into, big time, was canning vegetables,
My grandmother did this too, after living her childhood through WW2 (in Germany), she used to have a repository of canned vegetables in the cellar. I sometimes talked to her about her rural live in the war-torn country, and she told me about soldiers, and all kinds of people, who would come by in war-time, where food was very sparse. And I think she maintained that sort of hoarding behavior throughout her life, based on the experiences she made as a child.
Interesting. Our (my part of the US) rice is mostly sold in small plastic bags (perhaps 1-2kg), or for some brands hard plastic containers; larger amounts come in either a much heavier opaque plastic bag (like pet/livestock feed, when it's not in a lined paper bag of some kind), or a thin clear plastic bag inside a rough cloth bag. If there are already-vacuum-sealed options here, I've not noticed them.
Reading some other comments, it is also possible that these bags aren't actually vacuum sealed. It is hard for me to tell how much of a barrier you need to get a good sealing, in particular to protect from rice weevils (bugs), which appear to be the biggest issue.
"What they were into, big time, was canning vegetables, and gardening (to grow stuff to put in the cans). Man, were they ever into canning vegetables."
I became aware of the world just as seasonal food availability was becoming a thing of the past—I remember significantly more seasonal variation, but only when I was pretty young—so this really stuck with me growing up. All those colorful jars lined up on shelves, all the gardening, all the boiling-of-jars, et c. All that work, and a can of the same thing was $0.29 at the store.
So I assume they all developed these super-similar habits for really great reasons. And since the ~1960s and earlier were just normally pretty similar to what a significant food shortage would probably look like now (at least in countries that will almost certainly be able to maintain adequate supplies of staples, like the US) it seems to me that might be a good first place to look. Stock up on canned veggies, worry less about the rest of it. Maybe get some chickens and plant some berry bushes (they also all loved keeping a line or two of berry bushes, and it seems like in their generations you just alway kept chickens, if you weren't smack in the middle of town)
I'm going to ramble a bit... I grew up on a farm in the actual middle of nowhere. It was a then-defunct, mid-size dairy. In it's heyday it had 300 head of Holstein being milked.
My mother, whose parents ran the dairy, and to a large extent my father, instilled this way of life on me at a young age. Growing up, we had a huge vegetable garden (they still maintain a 1/8 acre vegetable lot in their 70s, it's quite impressive, really -- and that's in addition to a 400 sq. ft. greenhouse I helped my father build and the rest of their lot that has fruit trees, berry bushes, etc.) but I was always in awe of the canning and the preserving. You grow all of this food but you only eat 20% of it fresh, canning and preserving the other 80%. But then, being so young I didn't realize that our meals consisted of vegetables/fruits that were canned or preserved years previously, of course. There was a strong communal aspect to it, too. We'd get oversupply from neighbors and/or give oversupply to neighbors.
Chickens, too. The farm had a coup. My parents had a coup (they gave it up in their late 60s -- my father grew tired of dealing with the foxes and skunks they attracted). It's something I want to do but where I live it's impossible. We're planning on a move where we can have a chicken coup and more space for growing food in general. I'd really like to preserve the heritage, as it were, and it's become more important as we start a family.
Also, I've dealt with corn and wheat weevils before. I actually did not realize that they also laid eggs on rice. I guess I assumed that it was "different" or whatever but thank you for highlighting that in other comments. I've got 50 lbs. of rice that I'm going to break down to smaller vacuum sealed bags this weekend. I've dealt with weevils at least a half of a dozen times in my past and it is not pleasant. I do not want a repeat of that mess, but especially where I live today.
If you vacuum seal it with mylar lined bags and some oxygen absorbers, it can last up to 5 years, which is a long time.
Oxygen will get through normal plastic vacuum sealing bags and ruin the taste and eventually nutritional content otherwise after a year or two. Mylar lining stops most of that and the oxygen absorber gets the rest.
The thick bags will also stop rice moths from getting through (they are able to get through most cardboard and thin plastic bags), and the lack of oxygen will stop their eggs from hatching.
