My most reliable loco of the modern era is an MTH GP40 in Reading colors, it is from the first run of these locos. It has on the chronometer over 1 year (!) of run time, the odo doesn't reflect this, around 346 miles, but I assume that whenever the power is on the layout it runs the clock, so to speak. This loco, whenever we have difficulty with the DCS will be found, start and run every time. Last year I brought it home to service it, before taking off the shell I tried to run it in conventional, it wouldn't because of a dead battery, even though it was found in DCS earlier in the day. It has the original 5 volt board, and has only had one set of traction tires. I shouldn't brag, because of the jinx, but no matter what it does, it doesn't owe me a nickel, and I would happily upgrade it to a 3 volt board if anything happens. As far as postwar, any steam loco is reliable, as are my GG1 and GP7/9 diesels.