"Should I drink it straight away?", "Shall I take it slow, to enjoy?, "Will it change after some time?", "Can I keep it forever , once it is opend?". These question are being asked, as long as people got their first bottle of whisky, and still drinking it bottle after bottle.
My experience is, that the whisky will change after a certain period. Even, once a bottle is opend, it might change after 6 or maybe 7 months. During the years it will change, and the speed of changing, will depend of the strength of alcohol. I remembered one time that I bought my first bottle of Macallan 10Y old at 40%, I was so fond of that stuff that I kept it for a period of 6 years, I really enjoyed that wonderful stuff. However after 6 years there has been quite a changing that took place there in the bottle, time after tim when I took a dram, the taste was changing a lot, when I finished the bottle after 6 long years there was only 2 inches of the contents left. It was quite interesting to see what realy happend with the whisky once the bottle has been opend. I experienced it time after time, and noticed that quality was also a major factor. If you have a good quality of whisky, the taste will change, but not that quickly, it may take a while before it realy changes. I remeber my bottle of 21Y old Bowmore, I still have it and there are 2 inches of it left in the bottle, and still tastes very good, although it has changed a bit, but it's still OK.(don't worry I'll finish this one very soon) So in a way we can say it will change, and depending on certain important factors, it can be from several months to several years.
But don't forget, that your very own taste bud will change after some years, you must keep that in mind.
If you wish to keep a bottle for a very long long time, just don't open it store it at a dark and cool place(15-18 degrees celcius), and open it when the right time has come.
You can do the same with opend bottles, just store them in a cool and dark place.....
Well this is my opinion of opend and unopend bottles...