Two times a month apart,I parked next to same late model Lincoln SUV with engine running AC on (90F) no one in car; still running aprox hour later! One month later same vehicle but owner was there when I came back from hospital; I made comment possible overheat condition floor above catalytic converters;owner said had to have AC for the dogs in car which I understand. Also is extended idle hard on engine valves?
Police vehicles idle for long periods of time so the answer is no . The converters have heat shields so that is not a concern either.
Thousands of vehicles are left running for hours each day without catching fire, I switch off several cars each day that are left running in the parking lot at work.
It doesn’t help the life of the engine and rubber or plastic parts under the hood but that is for the next owner to worry about, most people don’t keep their vehicles for ten years.
My major concern would be that no one is there to shut the car off if it starts to overheat or if the oil pressure light comes on.
While it’s a possibility - it would be extremely rare. If the car is properly running then it shouldn’t overheat and there shouldn’t be any oil pressure problems. During the winter - Some truck drivers still never turn their Diesel trucks off for days on end.