The vinegar is a good idea just 1 teaspoon of vinegar per gallon of brine. It really will help as a preventative of softening. But once soft, you're stuck so far as I know. LinuxBoy once mentioned some sort of ion exchange that takes place. The vinegar is supposed to give up it's ion, rather than the cheese. That's a rudimentary explanation, and the best of my recollection, so I could be off on some details. From personal experience, if I don't vinegar, cheese softens, if I do vinegar, cheese doesn't soften, it's that simple for me.