Walnuts and other nuts and seeds are full of healthy fats. However, these healthy fats can start to go rancid when exposed to air and light. To help extend the life of walnuts and other nuts and seeds, I prefer to store them in the freezer. Because of their high fat content, nuts and seeds do not freeze in the freezer but instead they preserve freshness. Be sure to store them in an airtight container as you do not want them to absorb any other flavors from the foods in the freezer. Store walnuts in the freezer for up to a year.