Why the early 'drink by' date on Deschutes' Stoic

Among the many great new breweries to come to Missouri in the last couple of years (Firestone Walker, Summit, and others) Deschutes was a welcome addition. I've really enjoyed their Mirror Pond and Black Butte, and have a bottle each of Abyss and Black Butte XXIII in the cellar for when the weather gets cold. The one I was really not expecting to like (mostly due to poorer reviews on here) was the Stoic, but I was really impressed. There are probably a dozen bottles still sitting on shelves around town here, but the best-by date is in early August I believe. This was the 2011 release and I picked it up in Feb., 2012. Why does a beer that's barrel-aged and 11% abv (and typically a style that does well with some age on it) have a suggested relatively short life-span? Their other big boys say 'drink after'; what makes this one different? Any thoughts, or experiences w/this brew with age? I'm on a tight budget, so dropping $12 bucks for a beer that's past its prime or subpar is not something I'd like to do, but if they're still good I've considered picking one or two to share w/family and friends in IL over Christmas.

Also, related question. This is at a local HyVee (a big grocery chain that I LOVE, and who treats their employees and customers like gold). If they're still there in a month (or any outdated beer) is it acceptable to ask the wine/spirits manager if he'll knock 'x percent' off of an outdated beer (even if I know flavorwise it's probably ok)?