Caviar is a perishable food, and an unopened can or jar can stay fresh for approximately 4 weeks, while an opened container will only stay fresh for roughly 3 days according to About.com. Caviar must be stored properly in order to retain its delicate flavors, which means being kept at a temperature between 28 to 30 degrees Fahrenheit.
It is very important not to freeze caviar in an attempt to make it last longer. Freezing can destroy the texture of the caviar. The coldest part of the refrigerator, or the very bottom drawer, is often the best place to store it whether it has been opened or not.