California-grown pistachios are excellent keepers when stored properly. Bagfuls have been featured in supermarket aisles since the holidays.
To keep them at their freshest, store pistachios in a refrigerated, airtight container and/or keep them in the freezer for long-term storage, according to the trade association for pistachio growers in California. Yet a bag of naturally tan pistachio nuts from Walgreen's was printed with the warning, "Do not refrigerate, unless in an airtight container." Well, that's putting a different emphasis on the same information.Once opened and kept at room temperature for four days, the pistachios would have lost crispness in any damp climate eventually. If the nuts are to be kept for a week or two before eating, I'd track down an airtight tin for either freezer or refrigerator storage.
To restore pistachios that have lost their crispness, toast the nuts at 200 degrees for 10 to 15 minutes, so say the California pistachio growers.