An unopened bottle of nonvintage champagne stays good for three to four years. A bottle of unopened vintage champagne stays good for more than 20 years.
Proper storage of champagne is essential to getting the maximum shelf life. Champagne should be stored upright in a dimly lit, cool place with a constant temperature. If champagne was refrigerated when it was bought, it should continue to be refrigerated until it is opened. When aged champagne is opened, it should be opened very slowly. If there is no fizzing sound and the champagne does not have bubbles when the bottle is opened, the champagne has gone bad and should be discarded.