Assuming you are using a 5 lb CO2 tank to carbonate and dispense beer, it should last you 6-8 weeks. This is based on dispensing 20-24 half barrel kegs of beer. Of course, this will depend on how much you use your kegerator. If you find yourself needing to refill your CO2 tank more frequently, then you may want to consider upgrading to a 10 lb tank.