I treat my base grains like crackers. A box of crackers stays fresh for a LONG time if you keep it closed. Leave it open on the counter overnight, and they get stale.
I pick up 55# bags of grain from a distributor. They have pallets full of the stuff sitting in a warehouse in Tampa, FL. No AC. They are not vacuum sealed bags, but they are sealed from the humidity.
Moral of my story: don't bother refrigerating your grains, but DO keep them sealed in an airtight (but not vacuum sealed) container.