Conventional wisdom says it’s okay to keep chicken stock in the fridge for quite a while if you bring it to a boil every couple of days, but that’s probably not best, in terms of food safety. To keep your exposure to the bacteria that love to live in stock to a minimum, you should cool your stock quickly, either by transferring it to small containers or putting the pot in an ice bath. If you don’t use it within a day or two, freeze it. Kelli2006 brings any stock, whether it’s been refrigerated or frozen, to a rolling boil for 5 minutes before using it. And as Bostonbob3 points out, boiling a stock reduces it a bit, thereby intensifying its flavors.