Your air conditioner shouldn't ever require extra Freon.  Because it is contained within the coils where it flows, Freon shouldn't escape. If you think your AC is leaking refrigerant, call a professional right away because it is the only way your AC might be low on Freon.
Homeowners should get familiar with the symptoms of low refrigerant since Freon leaks pose a serious threat to an AC system. If you see any of the following symptoms, your AC may be leaking refrigerant:
The AC runs nonstop but fails to chill the home.
Your vents don't blow cold air.
Your energy expenses are very high since the system is always running.
The refrigerant lines are covered with ice.