Collecting brass locomotives is sort of a sideline hobby of model railroading. Some run their brass locomotives on their layouts, others just display them in a case, or on shelves. Some collectors don't even have a layout but just collect and display.
There are a lot more brass locomotives made in HO-scale and O-scale than in N-scale. I do have one N-scale brass locomotive, a bipolar electric.
Keeping brass in a case won't prevent tarnishing, but it can prevent expensive locomotives from hitting the floor! To some degree, brass locomotives have sort of "gone out of style" due to increasing prices and the improvement in the detail available on plastic locomotives.
Do you have a layout, or are you strictly a collector?
Brass locomotives don't tarnish. They are varnished to prevent it.
As far as just having one or more for show, that's up to you. I don't have any. I can't imagine paying those prices for something I'm not going to run, and I wouldn't dare run something that cost that much.
Not a collector, but I have always admired the brass engines to the point I thought someday I'll get at least one. Kinda like having 1 gold coin. Anyway, I am an hobbyist of many things and have decided it's time to pursue trains. I have enjoyed trains since I was young. I have several cars for my yard and a couple steam locomotives. Now I finally have the time and room to start my layout.
i have some .. run the layout with medium-small ones, painted, nothing over six driving wheels ..
the rest , smaller and larger, are in the display rack, about half are painted ..and yes, i ran them for a bit, but 2-6-0, and 4-6-0 fit the layout better, as well as the ones on the layout are already painted and weathered, you can't pick them apart from the plastic ones, except for better detail ..the plastic i have is bachmann spectrum geared steam mostly ..[ actually most of my brass is steam as well ..]
I have a few brass locomotives that I run. I have the blue goose and atsf 3463 by tenshodo. Now that I’ve done the work to them I enjoy running them. I also have a brass pioneer zephyr from nickel plate products a west side e8 a/b set a hallmark sd7 and an offbrand gp7 that has a brass shell on a plastic body. Not sure of the make on that locomotive. I personally buy the locos to run them but when you run them you have to keep it in mind that they’re eventually going to wear out. So they don’t get a whole lot of running time but when they do I enjoy seeing a brass locomotive from the 70s running today