Sometimes I put a desiccant in with them, if I have it on hand. If not, I sometimes use rice in a napkin. They say that wheat was found in the tombs of ancient civilizations that were still good, so as long as it is not exposed to moisture and/or air, I'd say at least 10-15 years.
This winter, I'm trying some different varieties, White Winter Wheat, Triticale, and the old reliable cereal rye. I have plenty of the Red Winter Wheat stocked, so time to branch out. Mostly, I don't want the beds to get taken over by weeds, so growing winter grains does that and provides, food, and good compost to boot.
This is good to know. I’ve been concerned about stocking up any whole grain because of rancidity.