I didn't know people kept nut butter around long enough for it to go bad...
They do when they use six different kinds of nut butters at the same time.
I realize I have peanut, almond, almond-hazelnut, sunflower, pumpkin seed and sesame butters in my fridge right now. (None of them is going bad, but I buy the smallest jars).
I read somewhere that nut butters usually keep for 1 month though... that is way to short!