As an experienced sommelier and brewer, I can confidently say that leaving alcohol in a decanter for an extended period of time is not ideal. While spirits can last longer in a decanter compared to wine, it is still best to consume them sooner rather than later.
The primary reason for not leaving alcohol in a decanter for too long is oxidation. When a spirit comes into contact with oxygen, it can slowly start to oxidize, leading to changes in flavor and aroma. While some spirits, like whisky, can benefit from a short period of oxidation to open up their flavors, prolonged exposure can result in a loss of intensity and complexity.
Additionally, over time, the alcohol in the decanter can interact with the air, causing evaporation and potentially altering the balance of the spirit. This can lead to a less enjoyable drinking experience, with the spirit losing its intended character and becoming dull or muted.
Furthermore, extended storage in a decanter can also lead to discoloration of the spirit. While this may not impact the taste directly, it can be off-putting from a visual perspective. The discoloration occurs due to the interaction of the alcohol with the air and can result in a less appealing appearance.
In my personal experience, I have come across spirits that have been left in decanters for an extended period. On occasions where the spirits were stored for several years, I noticed a significant loss in flavor intensity and complexity. The once vibrant and aromatic spirits had become flat and lacked the depth they initially possessed.
To ensure the best drinking experience, it is recommended to consume the spirits from a decanter within a reasonable timeframe. While there is no hard and fast rule, I would suggest consuming the decanted spirits within a few months to a year, depending on the specific spirit and its characteristics.
While spirits can last longer in a decanter compared to wine, extended storage can result in oxidation, loss of flavor intensity, discoloration, and potential changes in balance. To fully enjoy the intended flavors and aromas of a spirit, it is best to consume it within a reasonable timeframe after decanting.