Store popcorn, unopened, in a cool, dark cupboard for up to three months. For longer storage, refrigerate or freeze popcorn kernels for up to a year to preserve their natural moisture and allow them to produce larger popped kernels. Popcorn packaged with oil in its own “pan” should be stored no longer than about three months at room temperature. Popcorn is best when eaten soon after it is popped, but ready-to-eat or opened popcorn can be stored in a tightly sealed glass jar for up to two weeks.