I bought some kimchi a few weeks ago, ate half the jar, and then forgot about it. I found it in my fridge yesterday and tried it. It tastes the same, but there isn't a date stamped on the jar. Does it go bad or should it be fine since it's fermented/pickled? 
A great resource for how long foods can be kept is Stilltasty.com.   According to them, commercially bottled pickles (and kimchee would fall into this category) can be kept after opening for one year in the refrigerator.  