I have a couple of new XO bottles and would like to know how long they are good for once I open them. Should I try to finish them as soon as possible or do I have a window where the cognac will not lose its quality? I remember reading somewhere that the quality of the cognac worsens after a certain period of time. Although I drink it at times, I’ve never had the higher quality bottles here at home and want to make sure I don’t ruin them. Any help is appreciated. Thanks.