Here is info from USDA website:
Corning is a form of curing; it has nothing to do with corn. The name comes from Anglo-Saxon times before refrigeration. In those days, the meat was dry-cured in coarse “corns” of salt. Pellets of salt, some the size of kernels of corn, were rubbed into the beef to keep it from spoiling and to preserve it. Today brining-the use of salt water-has replaced the dry salt cure, but the name “corned beef” is still used, rather than “brined” or “pickled” beef. Commonly used spices that give corned beef its distinctive flavor are peppercorns and bay leaf. Of course, these spices may vary regionally. Uncooked corned beef in a pouch with pickling juices which has a “sell-by” date or no date may be stored 5 to 7 days in the refrigerator (40 °F or less), unopened. Products with a “use-by” date can be stored unopened in the refrigerator until that date. Drained and well wrapped, an uncooked corned beef brisket may be frozen for 1 month for best quality. It’s recommended to drain the brine because salt encourages rancidity and texture changes. The flavor and texture will diminish with prolonged freezing, but the product is still safe. After cooking, corned beef may be refrigerated for about 3 to 4 days and frozen for about 2 to 3 months for best quality. Corned beef is made from one of several less tender cuts of beef like the brisket, rump, or round. Therefore, it requires long, moist cooking. Keep food safety in mind when preparing corned beef. It can be cooked on top of the stove or in the oven, microwave, or slow cooker. Corned beef may still be pink in color after cooking. This does not mean it is not done. Nitrite is used in the curing process. This fixes pigment in the meat and affects the color. Allow the brisket to stand for about 20 minutes after removing from the heat. This will make it easier to slice, and it is best sliced diagonally across the grain of the meat. The USDA does not recommend one particular cooking method as best. Following are methods from various sources. The cooking times are based on corned beef that is not frozen at the time of cooking. “Fork-tender” is a good indication of doneness, but use a food thermometer to be sure. Cook all raw corned beef to a minimum internal temperature of 145°F as measured with a food thermometer before removing meat from the heat source. For safety and quality, allow meat to rest for at least three minutes before carving or consuming. For reasons of personal preference, consumers may choose to cook meat to higher temperatures.
eta... The "use by" date on the packages are pretty generous. I usually just leave mine in the frig. I think the "use by" date can be a month or more. I made corned beef tonite for my Aunt & Uncle. She said she freezes her corned beef all the time... but I haven't tried it .