Originally Posted by
tentseller
I find Scotches and Cognacs does not have a flavorful change over long term opened bottle storage. I think it is very minor evaporation. I have been given some slow moving bottles by the in-laws to clear space for more profitable brands which still taste fine.
Agreed that the biggest change in flavor in an opened bottle will be due to evaporation. Proper storage with the cork kept wetted is critical to minimizing evaporation IMHO.
There can be minor oxidative changes over time to even distilled spirits; obviously, the higher the proof, the less "stuff" there is to oxidize (as ethanol isn't going to suffer oxidation as part of aging). And with more headspace in the bottle, there's room for more of the interesting flavor compounds to evaporate into the air and leave the whisky itself... but again, this should be very minor compared to the kinds of changes you see in most wines.