If it hasn't been pasteurized, it should stay good almost indefinitely since it's a fermented product. Well, I guess not indefinitely, but I've had some that didn't mold or go bad for almost a year. It just gets more pungent and fermented tasting.
Also, this may sound gross, but even when it molds, as long as it smells okay, you can skim off the mold and use as is or if you are worried about that kind of stuff, you can cook with it. The gone bad smell and the fermented smell are pretty distinctive so you'll know when it smells different. Sometimes fermented stuff will form "bloom", or a thin layer of mold on top and it's pretty normal.