Storage of Whisky.
Most single malts and all excellent blends have matured for at least 10 years. So the product is ready and matured when it's bottled. Different from wine it will not get any better in the bottle. So does it get worse? I think that with modern technology most bottles will be sufficiently closed so no air can come in.
If then the bottles are stored in a cool place (not too warm and not too cold) and are not exposed to direct sunlight, it is fair to believe that the whisky will stay okay for decades and decades. Provided they are always kept in the upright position to avoid any leakage. Personally I can't and won't wait decades to open my bottles. First of all I'm to old for that and secondly I want to taste my whiskies!
It's something else completely if you ask me if you can store whisky for a long time after having opened the bottle. Once exposed to oxygen the whisky might lose some of its original characteristics. In July I bought a bottle of Bowmore Enigma, a very fine Single Malt from the island of Islay. You will find it high on my list of favorites so far. One of the distillery characteristics is the skillful combination of not too heavy peat smoke and not too heavy sherry finish. However, we are now in November and the bottle contains less than half of the original 1 liter. This means of course more oxygen in the bottle. As a result, a large part of the original smoke is gone. It's still a fine dram but it's not the same whisky I opened in July. So I suppose it's best to finish the bottle in say three months. That's too fast? Then you could consider decanting the whisky into smaller bottles so it will have less contact with oxygen.
At all times however, keep the bottles (opened or unopened) out of the sun. Not so easy here in Brazil!!