If its a deep freeze it will last forever. Deep freeze temperatures will kill most bacteria in few days, cooking kills the rest. Flavors may change if its not sealed well and gets freezer burn (de-hydration). Russians have eaten Mammoths frozen in the permafrost for thousands of years. Newer refrigerator freezers don't store as long because they are not as cold and will run a de-frost cycle every few days which blows warm air through the freezer compartment.