if the compressor is relieving load then check the air gap of the clutch, it can seriously damage the clutch and in sometimes render the compressor useless and inoperative. Click here to get a clearer picture of what Im saying.
If the clutch gap is excessive it will slip when its warm, its not a regular sound. It you hear actual noise even with correct air gap in the clutch then your compressor is internally bad - usually due to low oil. In most cases compressors usually last a long time if every fail safe in the system is working like low pressure switch, high pressure blowout, system correctly sized etc. etc.
The biggest problem in Pakistan is lack of education of the A/C techs who are trying to pose as A/C technicians, in both home and auto.