The last line is the honest answer for most kitchens. Nearly all of this advice assumes a cool dark space, and a modern flat with the heating on does not have one anywhere.
I stopped buying sacks and started buying about a week's worth, and the waste went to almost nothing. The per-kilo price is worse and I am throwing away nothing, which is cheaper overall.
If you do have a cool spot, the sack is genuinely better value. Work out which situation you are actually in before optimising the storage.