I'm not trying to be facetious in saying, I used to find the 15 noticeably drier than the 12, and now I find it sweeter! I do believe these drinks change over time. As a natural product produced from limited stocks, this seems inevitable and is a plus in my book.
I may have to bring my current blend of the two to the next Gazebo as well! I did it about two weeks ago to try to maximize the best of each and it is very good if I may say.