I just read that it recycles itself inside the system, UNLESS the system has a leak. Now, I suppose the refrigerant can get old and has to have some new put in, but that's it. IOW, the refrigerant doesn't evaporate, only leaks out. So, if your A/C isn't operating correctly, like blowing warm air out, then it needs to be checked for leaks. A qualified A/C place can test the system and tell you how much refrigerant you have in it. If the refrigerant is low, then (supposedly) there is a leak in the system. The compressor in ours was bad and had to be replaced. We'd turn the air on and the fuse, controlling it, would blow.