I freeze rice and flours and keep them in the freezer until I use them. I keep all my nuts and dried fruits in the refrigerator. You could probably do the same with dried milk and buttermilk and dried egg products, I would guess.
The problem with keeping your flour and rice or anything for that matter that you truly will depend on is what if the power goes out for a extended lenght of time?
speaking of dried milk...I cannot abide the powdered milk in stores...but if you can get your baker to sell you some of the powdered milk they use - it’s very fine and feels like cornstarch - You can mix that up (takes good stiff mixing) and cool it - not many people will ever think it’s not ‘real’.
I did this with a large amt of sugar I bought but the freezer kind of gave it a funny consistancy although it works just great in recipes..bought about 150 pounds for under $9 per 25pounds.....