A properly operating system should not need to have Freon added regularly.
Needing Freon indicates that there is leak in the system (and is a sign of a problem).
In addition, the use of Freon (R-22) is being phased out in favor of the incompatible
refrigerant R410A starting in January 2010. After that point, the cost of recharging
systems requiring Freon will dramatically increase.
Our technicians can evaluate your system for Freon leaks and advise you on the cost of repair if applicable.
For more information, read the official information from the EPA -
http://www.epa.gov/ozone/title6/phaseout/22phaseout.html