Yeah I’m not a fan of brown rice.
Didn’t know that about oats though, thanks for that!
Sugar and maple syrup should be in good supply.
Sugar keeps forever, but can cake up. I store mine in 1/2 gallon size canning jars. The jars are somewhat expensive and like all glass subject to breaking. OTOH, they do hermetically seal, don’t rust, and critters can’t chew through them. There are pluses and minuses to every storage method.
Maple syrup, along with honey, are replenished naturally every year.