YOU: Once you receive the keg, it should be sanitary and able to sit at room temperature for 6 months (or more). However, the moment you tap it, you have possibly introduced microbiological contaminants, and the spoilage timer starts ticking.
you can't have your keg at room temperature. "Temperature is by far the most important issue when it comes to dispensing keg draft beer. Almost all draft beer problems are temperature related. Most draft beer brewed in the U.S is not pasteurized, so it must be kept cold.
Temperature The majority of the time, the beer inside your keg has not been pasteurized, so it's important to keep it cold. Conversely, draft beer that is too cold retains carbonation, causing the beer to taste flat because the true flavor cannot escape.
A good rule of thumb is that the shelf life for a keg of pasteurized beer is about 90-120 days (or 3-4 months), and unpasteurized draft beer will last about 45-60 days (or 6-8 weeks) when stored at the proper temperature. If the beer in your keg is passed its expiration date, then we wouldn't recommend drinking it.