School me on tobacco staleness. In the past couple months, I've been slowly working my way throw a few different tins of tobacco, all of which I transferred from their original tins into mason jars. I've noticed in the last couple weeks that the flavor and aroma of my Black House and Presbyterian mixtures have really gone off - flat, ashy, with the Black House lacking its characteristic BBQ-like sweetness, and the Presbyterian robbed of its citrus-like qualities. I don't think it's a question of being excessively dry, as the Presbyterian retains a hint of delicate moisture. Any idea what's going on, and how to either restore this tobacco or preserve future tins from this fate?