Jerry - I couldn't find a particular post that covered your question but from what I know (which isn't so much, really - so all this could be just the figment of my imagination!) the acid blend probably keeps indefinitely as long as it doesn't get damp. I would imagine the Tannin too is fairly shelf stable. Don't really know about the nutrient and energizer. The Pectic Enzyme I have heard does have a shorter shelf life - 6 months comes to mind??
Fair enough question for sure, and I'd be more than interested if there is a chart or something definitive.