Generally speaking, any machine which starts and stops regularly and only runs for a short period when running, will suffer some kind of failure before one which starts less often and runs for a longer period each time. The analogy here is between cars used mainly in town, and ones used mainly on longer journeys (motorways). I don't have to tell anyone that such a car can clock up huge milages on the same clutch, brakes etc, because they are seldom used. By the same token, the cambelt will last longer because it, too is subjected to fewer starts and stops.
A case in point was when Shore power supplies were finally installed on the tug jetty and we would shut down after each tanker movement and change over from ships generator to shore power. This changeover entails "blacking out" momentarily as it is not good practise to parallel with shore supply. Because of this, some pumps and a couple of belt driven vent fans would stop and require re-starting each time we left the jetty and returned. The belts began breaking quite regularly when the fans were re-started whereas before, when running continuously, they had lasted for years! It is odd that, in these days of almost universal trip computers, the car doesn't analyse the type of use to which it is being put and flag up when such a change is advisable. I know some manufacturers do this for oil change intervals.
