Pretty sure my evaporator core has a leak, super expensive to fix. Can I just charge it 3 times a year or so? Is this going to damage my car?
A/C systems that are run low on refrigerant fail faster than those that are kept full. This is because the refrigerant circulates to oil that lubricates the compressor. An un-lubricated compressor will wear out. So just after filling the oil will circulate normally but as the refrigerant level drops so will compressor lubrication.
Also it is less than ideal to leak R134a refrigerant into the atmosphere; it is a greenhouse gas.