Yes your systerm should never need a boost, if it does it means you have a leak in the chillers lines, and boosting it would only reqire another boosting, and so on. a good way to test if you have a leak is to mix soap with water and brush it on your lines if you see bubbles you have a leak.
I am from Canada so we have certian laws and such, but if you did find that you need a "boost" of freon then buy a piercing valve ($10.00) this gives you access (like a bicycle valve) to chillers refrigerant system when the manufacturers deem as to expensive to install.
However, the piercing valve is not really used to keep as a permanant valve, not sure of longeveity of the valve.