There’s nothing wrong with storing your brandy in its original bottle, especially if you have a fancy bottle and you want to show off the label.
It helps if the brandy stays a little on the cooler side, but the temperature won’t impact the brandy all that much so long as your home doesn’t get 80 °F (27 °C) or hotter. You don’t typically refrigerate brandy, but you can if you’d like!
Storing your brandy upright also decreases the odds that you end up with a spill on your hands if the bottle isn’t completely sealed.
You can write the date you opened the bottle on the brandy’s label if you think you may cut it close to that 6-month threshold. The amount of air in your bottle may have a small impact on the quality of the brandy over time. If you only have a few fingers of brandy left in the bottle, try to finish it within the next 2-3 months if you really care about the flavor. You may not notice a huge impact if you drink it after 4-5 months, though.
A decanter is designed to help open up wine by exposing it to a small amount of oxygen. This process doesn’t do anything for brandy. The only reason to use a decanter is if you don’t like random bottles sitting out around your home. If you have a cheaper bottle of brandy, a nice decanter is a great way to present your brandy without tipping others off that you’re drinking the cheap stuff.
If your brandy came in a dark bottle, set a small light down next to the decanter before pouring your brandy. This will make it much easier to see the neck of the bottle as you pour. You can use a clean funnel to make pouring easier if you’d like.
Your brandy may still be perfectly fine if you don’t get to it in 4 months. You may not notice much of a difference anyway. You will almost certainly taste the difference if you wait more than 6 months, though. A small amount of brandy may deteriorate a little faster than a nearly-full decanter. If your decanter isn’t particularly full, try to finish the brandy in the next 2-3 months.
The high alcohol content of brandy keeps it from developing bacteria or mold, but oxidation can break down some of the ingredients and damage the flavor. Once the brandy is exposed to air, the ingredients essentially start turning. This takes a long time to happen, but the oxygen will eventually ruin any non-alcoholic ingredients in your liquor.
Brandy is made out of distilled wine, but there may be a variety of other ingredients and fruits added to your specific brandy. There is no iconic brandy “smell” the way there is for gin, vodka, and bourbon, so you may have to trust your gut a little.
This is probably your best bet if the brandy isn’t in pristine condition but you know you’ll feel guilty about pouring an expensive bottle down the drain. Mixers and cocktail ingredients should mask some of the more questionable notes in the brandy.
