I only had my East Rail switching layout for about five years before selling it. Even though I didn't keep it, it provided me with a tremendous amount of enjoyment.
How long should a layout last? The short answer, and a not very helpful one, is as long as it gives you enjoyment. Why bring the subject up in the first place? Because it has a direct impact on the approach you take to layout design. One of the largest segments of the hobby is the person that’s wanted a layout for decades and, due to life circumstances (typically family and career), has never been in a position to make it happen.
When the stars align and the day arrives that having a layout becomes a real possibility, and it will, a sense of panic often looms over the design process. There is a sense that the design needs to be perfect, that you have been waiting decades and now that the time has arrived, you don’t want to “blow it”. Having that outlook is catastrophizing things a bit. Back in the day it was the norm for people to have lifetime layouts, ones that lasted decades. Hopefully we’ve gotten away from that. A layout doesn’t need to last forever to be successful, particularly for a first timer.
As a first time layout builder it’s impossible to know what you don’t know. You don’t know your true interests as much as you think you do. You don’t have a sense of how long various construction tasks take and how hard (or easy) they are. You don’t know where the subtle land mines are. The only way to find out is to dive in, make your mistakes, and learn from them. Be open to the possibility that the first layout only needs to last three to five years. In addition to the enjoyment of building the layout and operating it, the biggest gift will be lessons learned.
When it’s run its course there is zero downside to dismantling it and starting again applying the lessons learned. The cost of the second layout will only be a fraction of the first project because so many components can be re-used. Examples include: control systems, switch machines, turnouts, structures, trees, details, and rolling stock. You may even decide to use the same bench work footprint in which case the cost of lumber will be reduced on the second go around.
When you go in with the attitude that your design doesn’t need to be perfect, then you unburden yourself and are less likely to drift into the swamps of design paralysis. By that I mean the common quagmire of going years trying to come up with a beast that doesn’t exist, the “perfect design”. If you follow a few basic “best practices” whatever you come up with at least be buildable and trains will stay on the rails.
Minimum radius of 24” for four axle power, 32” for six axle power and longer rolling stock
Number 6 turnouts
Grades not to exceed two per cent
Maximum reach in distance of 27”
Parallel track centers no closer than 2” on straights, 2 3/8” at a curve apex
Use a template to make sure you’re drawing reflects the actual size and geometry of a turnout.
When you change your expectations towards “launching” and “learning” the pressure will be off and the day when you can actualize your lifetime dream will be much closer and more enjoyable.