if it is thirty years old it must be energy guzzler compared to the current version equivalent machines. The compressors equipped may be semi hermetic or hermetic reciprocating which is out dated even in developing countries.
Refrigerant must be either R-12 /R-22 which need to be phased out legally.
Manufacturers have differential rates for Maintennace contract up to 5 years and there after up to 10 years.
Hence if it has worked for 30 years by any stretch of imagination needs to be replaced.