I run the era I grew up in, in the town I grew up in. ICG and SOU, roughly 1980-1989. I do have some GM&O units that I will run, as well as Amtrak (F40PH on the Crescent). I don't remember seeing the NS painted units until after 1990, but since SOU is a predecessor railroad to the NS, I have NS equipment too. I have IC pre-CN days, and am roughly cutting off the absolute time to 1995 or so, when ditch lights weren't on all locomotives.
Most of my rolling stock are boxcars, covered hoppers, tank cars, piggyback flats, gons, and pulpwood/woodchip type cars, with the occasional well car or autorack. If I ever join a local club, I'll have some more recent stuff to run too.
I have some UP, SP, SSW, BN/BNSF/ATSF stuff too, because I was buying before planning, and it's always cool to have some newer stuff.