My workbench in my workshop is 30 inches. It is a good height for working on big stuff when standing. I sit in a low chair, too, so I'm close to the work when sitting and working on a model: I'm close to it then.
As for the benchwork on the layout. Mine is at an average of about 40 inches off the floor and higher. I like it higher rather than lower. I have three distinct levels of terrain, as shown.
