Most emergency call-outs are preventable, and the prevention does not require a technician. It requires a short routine that someone on site actually owns.
Weekly, by kitchen staff
Wipe the exterior and the bin door seal. Check that nothing is stacked against the air intake or discharge. Look at the ice: if cubes are getting smaller or cloudier, report it immediately rather than at the next service. Never store the scoop in the ice.
Monthly, by a supervisor
Empty and clean the bin properly. Check the drain runs freely by pouring water into the bin. Note the approximate time it takes to refill an empty bin — this is the single most useful early warning metric you can keep.
Quarterly or six-monthly, by a technician
Full clean, descale, sanitise, condenser clean, filter replacement and a measured production test against the machine's rating. This is where declining performance gets corrected before it becomes a failure during service.
Environment beats maintenance
No maintenance programme rescues a machine installed in a hot, enclosed space with no clearance. If your unit sits in a sealed cupboard or against a wall, correcting the installation will do more for reliability than any service schedule.