"I am thinking of now

The water wouldn't hurt flextrack with nickel silver rails and plastic ties but the HO equipment will probably be more sensitive to dirty or wet rail. Larger scale engines usually weight more so get better contact when running over dirty track. There would also be the question of how the size of HO trains fit with the Christmas village buildings. If I was running engines outside in the weather I'd look into onboard battery power to eliminate any dirty track problems, and larger scale is easier to find room for batteries so I'd be sticking with it....DaveB

Don't give up yet

Ross,

I too am a large scale modeler and what you describe is brutal on ANY SCALE trains. Consider the length of the loop you are running on. Then calculate the number of revolutions your train makes in one hour time slot. Now calculate the distance your train has traveled. Our club does several traveling shows (or used to before Covid) where we would run - 6-8 hours a day, but not continuous. The more expensive locomotives with metal gears have held up fine. The less expensive ones have not.

Tell us more about what you are doing, and we can provide better thoughts on direction going forward. Where are you located, and what kind of weather are you dealing with on average?  You said you were using brass track, but what are the diameter of the curves on your layout? Smaller tighter curves make the locomotive work harder. Are you pulling long trains, or just a couple cars? Are the cars lighted, adding drag to the train increasing load on the engine?

Quite frankly, if you are getting 5 years out of a locomotive in that use case, I feel like you are doing fairly well. However after providing a bit more detail, I would feel more comfortable providing opinions on your question. Feel free to contact me at narrowgauge@gcalejunkie.com.