Jacpac's are being discontinued through cdn tire and are on clearance right now for $20....these were initially over $100...they run off paintball tanks. So the time it would last would depend on how many kegs you're pushing through and the size of your tank. The jacpac comes with a 9oz tank. But these are more for dispensing.....not so much economical to force carb. But you could naturally carbed with sugar, and just use the jacpac to set the lid and dispense.
Great for travelling, as it cuts down the risk of knocking over your normal co2 tank(5,10,20lb) and busting your pricing regulator($50+).....For $20, you get the tank, regulator all in one.