To add onto the food preservation thread, which is unfortunately private.
If you're hoping to keep oats for a while, don't stock up on the rolled oats, instead get whole oats, and process(grind/roll) them as needed, they take half as much space that way, and will last a lot longer.
@neauoire I remember when you got (or were gifted?) that grinder; do you happen to have a model number or other documentation available for it if I were to look for a similar on the second hand market? This is one of those things I probably *could* find a higher-tech solution for, but don't *need* to
(Though I guess a burr-style coffee grinder, like the one I have, actually probably works for grains in a pinch. It's just a motor and blades, eh?)