While dry-roasted pistachios are a good source of protein, fiber, iron and magnesium, they don't keep forever. Store roasted pistachios in the refrigerator or freezer to prolong their shelf life. They can also be kept short-term in a cool, dry place such as a pantry.

Stored in a pantry or other cool, dark and dry place, a package of dry-roasted pistachios stays fresh for about six months; potentially even a few months longer. Check an unopened package for a "use by" date to ensure the nuts aren't already old when you purchase them. This stamped date is a good starting point to gauge how much longer the nuts can be kept at room temperature.

The key to keeping dry-roasted pistachios in a pantry is to ensure they are not exposed to heat during storage. In other words, keep them out of direct sunlight and away from the oven, stove top, heater or other source of heat. Heating could affect the oils in the pistachios and make them turn rancid.

A refrigerator is a better place to store dry-roasted pistachios if you don't plan to eat them all right away. Package them in an airtight container to store them for up to a year in the refrigerator. An airtight package helps prevent condensation, which is not good for the nuts.

A freezer is an even better option for long-term storage because the nuts will keep their flavor better than in the refrigerator. Dry-roasted pistachios stay flavorful for at least one to two years when properly frozen. To freeze, package the nuts in a freezer bag or airtight container. When ready to use the pistachios, allow the entire package to thaw to room temperature, and then remove what you need from the package before returning the container to the freezer. The nuts can be thawed and refrozen multiple times, unlike many other foods.

If the pistachios seem limp after thawing, placing them in a 150-degree Fahrenheit oven for 10 to 15 minutes restores their crispness.

Besides using time as your guideline for good nuts, a taste test is the true way to determine if those pistachios are still edible. The natural oils in a pistachio can go rancid if the nut has been exposed to too much heat during storage.

If pistachios smell bad, roasted or not, throw them away. Sometimes they'll still smell fine even after going rancid. Tasting them is the only way to know for sure. If a taste test determines those pistachios are putrid, throw them away, including the piece you've sampled.