Sorry Ken, I think that I have hit that point. Not having the space you have and having started my layout over 25 years ago, locomotive wise, I think I have enough, if not too many.
I have my fleet of Alcos that I have custom painted. When I started the layout there weren't any Northern Pacific locomotives on the market that were affordable and had a correct paint job. I custom painted a few and finally there were some good ones on the market and I did get a few. The same goes for the Milwaukee Road. Few accurate offerings so some were custom painted until commercial offerings were available.
Now that the last yard is in operation on my switching layout and I have been able to operate as planned at the beginning of the build, I don't have enough room on the layout for all the power. I also have a few brass locomotives that are too large for my 90 foot turntables and really wouldn't have shown up on a short line railroad, such as a Challenger ot the NP Z-5 Yellowstone (2-8-8-4) and a couple pf others. They live in their boxes and are taken out a couple of times a year, lightly lubricated and run for a while to keep things moving.
Freight cars. I can fill both yards, have all industrial sidings full and still have enough freight cars to keep a couple of 20 or so trains in hidden staging tracks.
Yes, I do have enough. . . . . . . . . . . . BUT, I have been picking up Kadee freight cars from Amazon for eastern railroads which I realized that I had very few of.