Ferrysteam said:
There are a lot of factors to take into consideration before condemning a steam loco as being inefficient.For instance,how long does a steam engine last compared to electric or diesel,well maintained ,100 years?.How much damage to the track is caused by electric and diesel compared to steam,a lot more,I know.On top of that,steam is much easier to maintain and build also much more beautiful in motion.
Electric motors have a long life span. When the Southern electrified with third rail the motors from the first batch of multiple units were used on their successors. Skimming the commutator and replacement brushes is all that is needed.
I think it is much the same with modern electric motors. Near where I live is a firm dealing in second hand industrial electric motors. The bigger ones are often stacked up outside and I have recognised some made 40 years ago - I helped make them. They were not traction motors but drove big ventilation fans. They were also AC synchronous so no moving contact parts.
I do not know about diesels, but I suspect that if maintained regularly they can go on forever, or at least as long as a steam engine.
Modern kit when properly looked after can last as long as one wants. At least one of the Chinooks in Afghanistan also served in the Falklands, not exactly an easy life, but obviously good maintenance.