Hi Arnold, I'm not even sure I know what "in moderation" means, in the context of our hobby.
I say that judging from my own approach, and having seen numerous other ventures into this hobby by fellow-hobbyists, via in-person visits to layouts, as well as through reading myriad magazines.
It seems to me that all of us approach immersion into model trains by pushing for as much space as we can absorb for constructing a layout, using as much of our leisure and relaxation time as we can to accommodate building a layout and/or collection, and allowing as much funding as we dare for the zillions of "must-haves" within our voracious appetites for train fun.
Regarding my own immersion (moderate?) I asked my new bride, back in the mid-90's, once we had "finished" furnishing and decorating own new 9-room house, if we were finished, AND if she would be comfortable with my utilizing much the basement for construction of a model train layout. Ever the adventurer, she replied in the affirmative in both regards, and so I began my basement journey.
First, I ordered 20 pre-cut 4'x8' sheets of lumber, finished on one side, and 2x4s for frames and legs. Then, once the lumber was delivered, my reaction was to be totally intimidated by the size of the load that was delivered to the driveway of our house, and proceeded to pretend I knew what I was about to do.
Apparently, pretending is a large part of this hobby, especially when launching oneself down the road of crafting a layout.
Eventually, I figured it all out, thanks to plenty of solicited-advice, as well as due to not being afraid to make mistakes and re-do anything I had thought twice about.
My wife even helped me upright the first 4x8 section of the layout (the first of twenty such constructions.) I was thrilled and on-my-way. She even joined in - when she could get past my heaps on her way from the cellar stairs to the door to the garage - with the creativity involved, offering the occasional reaction to the developing layout as a non-hobbyist (which was temporary!) For example, it was she, following an early interpretation of the layout having been shared with guests, who "inspired" me to remove a turntable, roundhouse, and yard, by saying, in her own inimitable style, which included a sweeping gesture with one arm, "Get rid of this." And I did, replacing it with the entire neighborhood seen here.
As the years progressed, I concluded I had a moderate layout and a moderate involvement in our hobby. It was moderate and sufficient for me; for us.
As I went along, I simply reminded myself that I was at-play, giving myself permission to immerse myself as deeply as I could go. Was it moderate? Compared to whom? To what? I have no idea. I'm just glad I am still knee-deep in this hobby of ours (literally and figuratively), especially every time I walk down the stairs to the basement, or enter the house from the garage, and see the layout spread out in front of me, and walk past it on my way outside or inside .
When I am in the frame of mind and of heart to play once again, I will turn all ten loops of trains on and perhaps even invite others, once again, to come to Moon Township, USA, to play.
FrankM, Moon Township, USA