Smirnoff bottles do not have an expiration date; vodka can last indefinitely if the bottle is unopened. It would take decades to affect the flavor of the drink. If the bottle is open, the vodka evaporates faster, but it does not go bad.
The proof may dip below 25 percent after a few decades, which increases the possibility of bacteria or yeast developing in the bottle. If the vodka develops an off odor, a strange flavor or a change in its appearance, it should be discarded. Vodka should be stored in a dark place and not exposed to any extreme temperatures. It should always be sealed tightly with the original cap.