The homebrew club I’m in collectively had 6 years of Abyss bottles so we did a vertical tasting tonight. We had years 2007 through 2012, every year they made it except 2006. Our 2009 was also one of the famously Brettanomyces-infected bottles.
All were great, of course, but I liked 2010 and 2011 the best. They still had the distinct coffee and chocolate tastes I love in Russian Imperial Stouts. The flavors in the older ones were more blended together and the 2012 hadn’t developed enough. And I really liked the Brett 2009, it was very unique but not nearly as sour as a typical sour beer. They should make a Brett Abyss on purpose!