I've had several bottles that seemed to change significantly after being open for a period of time. The flavors seem condensed and dull upon opening the bottle and seem to expand with aeration. I've always attributed this to some aspect of the bottling process. That said, I also acknowledge that there may be a psychological component at work wherein my expectations of a bottle change over time or a change in my palate enables me to tease out flavors that I missed before. As others have said, a blind tasting would be the only way to put the debate to rest. Most of my bottles are singles so a direct comparison isn't an option here.