Grains that have less than 10% moisture and are low in oil are best suited for longer-term storage. If your storage conditions are ideal (here is a link to a past post on ideal storage conditions), then some products can be stored for 30 years or more. This can give you a lot of time to rotate and replace your storage.
It's good to be educated about which grains store well and which don't so that your long-term storage doesn't spoil in just a few years. The following foods are NOT recommended for longer-term storage because of their moisture or oil content:
(Source: The Church of Jesus Christ of Latter-day Saints: Provident Living)
Whole Wheat Flour
Milled Grains (other than rolled oats)
(Some additional dry products that are NOT recommended for longer-term storage are brown sugar, nuts, dried eggs, and dried veggies and fruits)
Provident Living (The Church of Jesus Christ of Latter-day Saints) has published this new list of longer-term storage products and their expected "life sustaining" shelf lives:
Recommended (Life Sustaining Shelf Life Estimate):
Wheat - 30+ years
White Rice - 30+
Corn - 30+
Rolled Oats - 30
Pasta - 30
(Some other dry products that store well long term are sugar - 30+, pinto beans - 30, potato flakes - 30, apple slices - 30, powdered milk - 20, and dehydrated carrots - 20. "Salt, baking soda and vitamin C" tablets also store well.)
This is a great article which discusses the research into shelf-life in depth:
Home food storage lasts 30 years or more.