The shelf life of Martell Cognac varies depending on storage conditions. While eaux-de-vie can be aged in oak casks for several decades, once the Cognac is bottled, certain steps are necessary to maintain its quality.
Unlike wine, Cognac doesn’t mature further in the bottle. However, if stored with an intact cork and without excessive exposure to air, a bottle of Cognac can last for a long time.
Note that the more air in the bottle, the more it may subtly alter the flavor of your Cognac. While open, Cognac can remain drinkable for months, but you may notice a gradual change in taste over time.