Diesels
Numerous tests are carried out by all manufacturers of both stationery and "moving" engines.As a qualified person I can say with certainty that the average diesel or petrol engine would have absolutely no problem running at WOT for hours as long as it was properly cooled and was being held inside the parameters laid down by the engine builders with regard to safe RPM at max power.35-40% at cruise is easy going;In fact,engines prefer to run at various loads from low speed to full power and prefer to run in extended cycles which reduces wear.A typical diesel will have a max operating limit and a continuous limit.Generators run thousand and thousands of hours without shutting down--or just for an oil change.
I seem to recall that someone in the US is fitting a Corvette V8 to a light aircraft.
Someone mentioned that the VW V10 diesel has been a bit unreliable and it has been so;The gas version is fine.
Interesting discussion this-----I actually have a diesel in one of my Yachts which has run 13,000 hrs with ONLY oil & filter changes at max continuous revs---not even injectors or pump.Had this diesel been installed in a truck travelling at 100 km/h it would have covered an awesome amount of ground......Gasoline engines on the other hand do not last nearly as long but are seldom subject to catastophic failure-----they will just start using oil or maybe burn a valve.Engines have come a long way......