We recently had an air conditioning unit repaired. When had done the job, the guy asked when the last time was that we had our units serviced, and looked shocked when we said we never service them; all we do is clean out the dust filters. He says we should service them at least once a year, otherwise parts are liable to get damaged. Of course, the fee is no small amount; it's a significant percentage of the cost of the unit itself, and we have 8 units in the house.
We've had our units for several years, and none of them have ever been serviced, nor have they ever broken down for lack of servicing. Have we just been lucky, or is there no real need to service these things?