I'm not sure how many run them outside for display for the public at their homes. There are definitely those that run them in public displays in malls and some outside.
Theft could be a problem depending on the area.
Another item of concern is wear on wheels&wheel flanges, gears, track (if brass track).
if the engine is diesel like by USA Trains or Aristocraft it will have plastic gears which will eventually wear out. USA trains replacement axles/gears are always readily available and replacement is pretty easy. Aristocraft parts arent available and because of difficulty in repair, you would want to replace the whole motor block. I wouldnt use Aristocraft for this application. MTH diesels have all metal gears so those should last much longer. But eventually motor bearings etc will wear out. You will want to regularly lubricate axle bearings and even motor shaft bearings I would say once a week at least.
Brass track on public displays is known to wear out in curves. So I would go stainless steel.
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