As an expert sommelier and brewer, I can confidently say that unopened bottles of brandy can last indefinitely if they are sealed properly and stored in the right conditions. Unlike wine, which can continue to mature and develop flavors over time, brandy's maturing process stops once it is bottled. This means that you won't notice any significant changes in flavor or quality as the years go by, but on the flip side, it also means that the brandy won't degrade if stored correctly.
When it comes to storing brandy, the key is to keep it in a cool, dark place. Temperature fluctuations can have a negative impact on the quality of the spirit, so it is important to avoid storing it in areas where the temperature can rise and fall dramatically. Ideally, the brandy should be kept at a consistent temperature of around 15-20 degrees Celsius (59-68 degrees Fahrenheit).
Light can also be detrimental to the longevity of brandy, as it can cause oxidation and spoilage. Therefore, it is best to store the bottles in a dark place, away from direct sunlight or any other sources of UV light.
Another factor to consider is the bottle's seal. A properly sealed bottle will prevent any air from entering and affecting the brandy. It is important to ensure that the cork or cap is tightly sealed and in good condition. If the seal becomes compromised, it may lead to oxidation and a decline in the quality of the brandy over time.
In my personal experience, I have come across bottles of brandy that have been stored for decades and still tasted exquisite when opened. The key is to follow the guidelines mentioned above and exercise caution when handling the bottles to avoid any damage to the seal.
To summarize, unopened bottles of brandy can be kept indefinitely if stored properly in a cool, dark place with a tight seal. While the brandy won't continue to mature or develop flavors, it also won't degrade if stored correctly. So if you have a special bottle of brandy that you've been saving for a special occasion, rest assured that it will be just as enjoyable whenever you decide to open it.