Both shelled and unshelled peanuts should be kept refrigerated in tightly sealed containers. Unshelled peanuts will keep for up to nine months in the refrigerator, while shelled peanuts will keep for up to three months. It is important to discard peanuts that are discolored or even slightly moldy or rancid since they can be easily contaminated by aflatoxin, a mold that has been linked to cancer in laboratory animals, though not in humans.