Here's one for my fellow foodpicklers: The LA Times kitchen tip this week suggests saving Parmigiano cheese rinds to toss into a soup or stew, which I already do. But the tip recommends freezing them until needed. What if you haven't frozen them? How long will they last refrigerated? I have some that are pretty long in the tooth -- can I still use them in a soup? They're not moldy, just really old.