Well I have a layout that is 30 years old. Wood warps and shifts and swells and bumps happen despite my best attempts. When running 25 car trains that are quite heavy, especially on a 1 1/2 percent grade, couplers that only mesh halfway are often real culprits for causing train breaks. Remember the couplers also move up and down some in the box. When under load they tend ride one way or the other, most times it seems up.
The way to avoid problems down the road is to build things right at first so you don't have problems later. Setting the couplers right to begin with is a pretty easy standard to improve longterm operations.
