Surely premature maintenance issues are also a significant impact to earnings too?
That is taken care of by providing guidance on how long the engine has to be at idle prior to shutting it down, ie a cool down period. It's dependant on whether reverse was used etc.
i.e. What's the difference between starting an engine then within seconds or minutes, going to takeoff power AND starting it, let it warm up during taxi/(runups) then taking off?
There is also warm up guidance prior to a take off but I am only talking about se taxi on arrival at destination anyway.