P51 has it right, loops are boring and interest is lost quickly. My layout is 38 yrs old and I am still adding features, latest was a operating gantry crane. I just added another track around the turntable. I also picked up a couple of 4-4-0 Generals after turning my nose up on them for years.
My layout was designed to be complicated and is full of action, all to keep it interesting and challenging. Three transformers, five train operation at a time (two per circuit via relayed blocks), 27 switches, turntable, and at least 10 operating accessories. The layout is in the middle of the room with tracks everywhere. I am always getting ideas to add, change or improve the layout.
Model trains are not my only hobby and they get more attention in the winter. For years the layout was on the floor in the family room from Nov until Mar or so. Trains is a part time hobby for me and I enjoy fixing up cars engines and making improvements as much or more than operating.
Charlie
PS I plan to start a thread on my layouts evolution over the years soon.