Have to be careful how you define "wear out." Having written a book about aging electric equipment and when it is "worm out" I will use my definition there: It is worn out when it is not repairable or not worth fixing.
I have worn out a Lionmaster Legacy Big Boy. About 800 hours a year of running for three to four years. The electronics still worked except for one minor problem that I could have fixed, but mechanically it was loose throughout and I put in on the shelf . . . I had a WBB Trainmaster that had about 1500 hours on it and burned out two motors (about a year apart) during that time, the first i replaced and when the second one blew I did not replace it - figured there was something wrong with this (can motors just never fail on their own unless you abuse them and I wasn't - I figured something in the loco was!).
Lionel conventional Hall class (like the Harry Potter train only this was Hallows Eve) - I overloaded it (it has a small engine) and the board actually died not the motor). I took it apart for parts.
More remarkable is, have you ever seen someone wear out track? The folks at my local LHS ran a ceiling train all the time and it eventually worn away the metal entirely from the inside of O-27 track in some of its curves!
Wow, that is a lot of hours of running!
Lee,
What would you say are your most reliable, best, and enjoyable running engines and sets that you run in conventional mode?
