Bob Brown, narrow gauge modeler and owner of the Tuolumne Forks model railroad has written in his Narrow Gauge and Shortline Gazette about choosing a good concept for model railroads. Brown had about a year to develop a concept for his Tuolumne Forks railroad and it was hard for him to decide what he wanted to do. He started by placing a simple dog bone type layout to fit about half of his modeling room.
This left the rest of the room so that he could follow a different concept later on when he made a decision. He eventually filled the whole room with his layout. Brown has built two 2 foot dead-on accurate scenes. One being Wiscasset in Maine and the other Phillips on the Sandy River. After building these scenes, Brown discovered that he couldn’t maintain his enthusiasm if controlled that much by a prototype.
He found that the concept right for him would give him enough breadth and room for creativity, and with that indefinable atmosphere. Too broad or big of a layout is hard to keep up work on, and too limited of a concept produces the same problem. For Brown, a good concept is one that keeps a modeler inspired to keep working on the layout for long hours and over years.