About a year and a half ago I chainsawed my HO layout to make room for a more serious arcade. My plan has always been to take what I learned from that layout and build a much better one.
What I love about model railroading is that there are always about two or three thousand projects of varying size that you can jump into whenever you have the right amount of time and energy: Tuning up a boxcar can take 15 minutes, and building the benchwork for your extension can take a couple of days. Same with expense. You can use the free dirt from your yard, or you can invest a couple thousand in brass locomotives.
I always loved building with "unofficial" materials, like the cheap gravel from the fish section of the pet store, or making mountains out of foam insulation. It's a very relaxing hobby with a lot of different paths to take. The only part I wasn't too keen on was that there didn't seem to be too many younger folks getting into it. There were a few here and there, but I am afraid there might not be much future to it in another generation or two.
Also, I found this odd: A lot of model railroaders seem to be named "Don". Strikingly more than I generally run into in regular life. I have no explanation for that.