Brandies, like many other spirits, are aged for years in wooden barrels (around 15 years for Cognacs), during which they take on many of the aromas and flavors of the barrel. However, once they are bottled, the aging process stops and there is no maturing to speak of, unlike wines, which continue to develop flavors and texture in the bottle. As a result, brandy is a stable spirit once sealed and bottled,

As long as the brandy is stored in a sealed, unopened bottle, it will keep indefinitely and would be perfectly drinkable decades – or even more than a century – later. In the absence of additional air, and preserved by the high alcohol content, the spirit remains in a suspended state where no further chemical changes occur. As an indicator of brandy’s longevity, the Lanesborough Hotel in London purchased a bottle of Cognac dating from 1770 to serve in one of its bars, while the oldest intact bottle on record dates from 1738.

Once the bottle is opened, the introduction of fresh oxygen sets chemical reactions in motion, which ultimately leads the brandy expire. The brandy will be drinkable for up to a year after opening, according to the Beverage Director for the Brandy Library, and can never “go off” in the sense of coagulating, molding or developing toxicity. However, there will be a noticeable degradation in flavor and quality as the alcohol starts to evaporate and the spirit oxidizes to render an insipid, flat version of the original.

Avoid storing brandy in warm conditions, where the evaporation of alcohol and oxidation will occur more quickly. Crucially, brandy should be stored upright, to avoid the accumulation of sugars around the cork which will then infuse the spirit with flavors from the cork. Again, this is a departure from wine storage, where a vertically stored bottle risks drying out the cork and causing oxidation. Transfer the brandy into a smaller bottle once there is a significant pocket of air in the bottle to slow down degradation.