The one caveat to aerating a full bottle of an older vintage wine by decanting it is that the wine should be drunk within the next 30 minutes to one hour. If not, it may oxidize quickly like a freshly cut apple turns brown.
Some very old wines may start to oxidize within 30 minutes after opening the bottles and decanting them, so bottles to be decanted should not be opened for hours before being consumed.
In an aged wine, any remaining antioxidants are on their last legs and the large infusion of oxygen will quickly overwhelm them and almost immediately start to break down fruit chemicals.