Only a couple of times, and that was because the blend was about to disappear. Stocking up in this instance meant 5 tins, hardly a massive buy. At worst I figured that I'd be stuck with them, or possibly be able to trade them. And, I knew the blender and had an idea what I was likely to get.
My biggest error was buying a stack of Germain's reissue of Balkan Sobranie when it first came out. I'd smoked a lot of it in the 1970's and early 1980's and since it was Germain's I figured how bad could it be. I found out.
But generally I don't stock up on anything I haven't tried. Part of the problem with your plan is that you're buying blind and may find yourself with a lot of tobaccos that you don't like, and may not be able to trade off, or sell off at par. You do have some time before the fecal matter potentially hits the spinning blades. Why not try out a variety of blends now, before you commit?