Completing a large layout is mind over matter. I started construction of my layout in 2006 and finished it in 2011 (although one continually tweaks it). For most of this time frame, I commuted over 1,000 miles and I made the most of the weekends I was at home. During this time frame I had a very busy work schedule that required some weekend travel to conduct training session across the USA and Canada.
Like Elliot, health issues can put a damper on the progress of a layout as large as his is. I was fortunate during my construction where I had one surgery that took me out of the game for about a month. The key for me was the fact that I was mission orientated and I was determined to finish this project.