Everything has a shelf life, even Twinkies. I have used stick fast until recently (changed because I moved and Rockler and Woodcraft are too far away and I can get BSI within 5 miles). But as far as changing there formulation they may have, or one of their suppliers changed one of the things they purchase to make stick fast ( this happened to us all the time in the ink business, all of a sudden things would get all screwed up just to find out are supplier changed something and they didn't tell us) or maybe they couldn't get the ingredient they used to and had to use something else. Anyway, I too used to leave my stick fast uncapped for a long time, like a year with the large bottle, and before I changed around the first of this year, I also was throwing away bottles because they got thick and didn't seem to cure as well. So I would say yes, something did change.