I have been giving my scale Polar Express a real workout over the last month. Last month, I ran it at a Greenberg show for nearly 6 hours straight two days in a row, and since Thanksgiving, I have been running it 4 hours straight on the six nights (so far) I have gone to the Pittsburgh Independent Hi-Railers setup at a local amusement park's holiday light display (Kennywood Holiday Lights). No problems so far. Looks like the scale Berks are as well-made as the 1:1 models.
Andy