The Limits to Growth
Yes, preparing stuff for the layout when you are away from the layout is a great use of available time, whether it is pre creating the layout or because you are travelling. When I was doing far too much work-related travelling, I always took along a couple of detailing or construction projects that I could work on in a hotel room. You can get away with a surprisingly compact travelling toolkit, too. I work in N scale, and it is astonishing how much of anything it takes to fill even a classic wide open space to achieve a measure of realism. You can put a lifetime of modelling into a cityscape or a well treed, mountainous landscape. Someone mentioned people on the layout - painting thousands of N scale figures to even the most basic of standards can consume huge numbers of hours. Definitely something to tackle for an hour here and there whenever the mood takes you, and you have the opportunity. Even fifteen minute sessions with a single colour and brush add up surprisingly fast and can partially cover a whole lot of miniature figures on the spur or in a multi-figure jig.
I also endorse using jigs for hand-laid trackwork, because when a layout grows large, ultimately maintenance becomes the limit to growth. Everything requires maintenance, and this is true whether you operate frequently or infrequently, and no matter what measures you put in place to inhibit decay (or reduce entropy). Even the most carefully laid trackwork will eventually develop problems, and problems always take longer than you would like to fix. In fact, detecting problems also becomes an issue in preventive maintenance, because it is really unfortunate to find yourself using operating sessions (especially those involving other people) to find your problems, and then having to try to rectify them in fast clock time.
Some of us prefer to do everything ourselves, working alone, which is a personal choice, but comes with automatic limits to growth from the time available to you. Many hands really do make light work, and the layout will benefit from input by others, not to mention the pleasures of congenial company while working on a shared project. In any community with a population of more than a few thousand it is almost certainly possible to find people who will be delighted to help you out, often because they as yet aren't in a position to have a layout of their own. Think of it as informal clubbing.
My current N scale monster in progress (eighteen years and counting) has benefited from three classic principles:
(1) Take the time to build everything as carefully as possible, to minimize the maintenance needed down the line, so to speak. Working incrementally as much as possible, test every component as thoroughly and as soon as you can until it is as near perfect as makes no difference. It really helps to have well-documented standards for everything, too. Once you are there, add the component to the appropriate maintenance schedule. This really does pay big dividends over time.
(2) Come up with careful and detailed maintenance schedules for everything: benchwork, track, electrical, scenery, locomotives, rolling stock, lighting, signalling, control systems, sound systems, animations, DUST... Everything, and stick to them. Simply creating these schedules gives you a fair idea of when you are heading into territory that is too big for your available resources. It is no fun reaching the point where you can't work on new projects because every available moment is consumed by maintenance. And skimping on maintenance simply doesn't help, because when you do finally get to it, it will take longer and cost more, of everything. Just remember, everything has a life cycle, it is just the periodicity that varies: you may only need to look at some things once a year, but others much more frequently. Hence the need for documented schedules.
(3) On a large layout, look to what you can automate. Jigs for hand laying trackwork are just one example. I am a lifetime techno-nerd, so I make heavy use of computers and sensors to run diagnostics of many kinds. For instance, I have a multi-car cleaning train that does a pretty good job, and I have a computer program that manages track coverage with it, with a companion program to remind me of the stub tracks (and other tracks the cleaning train can't cover) that are (over)due for some personal attention. I have also developed (well, am continuing to evolve) an automated track inspection system built into a couple of 60-foot baggage cars. The sensors available today are incredibly compact and powerful, and with the right software can do an astonishing job of picking up irregularities in the track from simple mechanical motion and basic electrical sensing. No, I have NOT tried to do this with lasers, thank you for asking! But consider for a moment what's built into a typical smart phone today, and that's not a big package.
Yes, my layout is too large for me, but I am stubborn, and get so much fun out of it that I am probably addicted. And I can always dive into the software to try and improve my life on the railroad, an activity which I find just as pleasurable, as well as being complementary to the model railroading.
Remember, "just because you can" is neither a good nor sufficient reason for anything. But, as has been said in other contexts, size has a quality all its own. If you really want a big layout, go for it.
OrlandoQ