What maintenance tips can extend the life of commercial refrigeration systems?

I visited a supermarket service shop two days ago to learn about commercial refrigeration maintenance I wanted long life system I wanted low breakdown I wanted stable cooling but I got confused fast Some machines look very strong but still need frequent cleaning Some feel modern but service cost is high Some systems are quiet but parts are expensive I checked few units and it looked okay but not clear how to maintain properly I could not trust advice fully I could not decide confidently.
Then I visited another technician in same area Some say cleaning coils is most important Some say door gasket checking matters Some say refrigerant level must be checked Some say airflow should not be blocked Worker say most breakdown happens due to poor cleaning not machine fault I remember one store where fridge stopped cooling because dust blocked condenser That make me hesitate more I is thinking maintenance is more important than brand sometimes.