Our museum open houses run four hours every two weeks. The same train often runs for the entire time with no problems. I would echo the recommendations to make sure the trains are cleaned and lubricated (rolling stock as well, you don't want a loud squeak), turn off the smoke units unless you are prepared to refill them often, and bring spares.
The two trains you are suggesting should be fine. Some early TMCC engines and almost anything with QSI electronics can overheat if they are run too long or with too heavy a load. QSI reverse boards are notorious for melting if overloaded.
