Some of what you describe sounds to me like there may be subtle defects in the model itself. Vanishing is often an indicator that there are remote entities that affect zoom-extents operations. They might also affect printing, I suppose.

Peter A test scene would be interesting, but would probably have to be developed with a specific test in mind, or contain layers that could be turned on progressively as the test goes on. In my experience, shadows, poly count and scale are the things that can cause difficulty. I always have the shadows off or at least have created a scene where they are on that I can reference to. Poly count, that's hard especially when something like trees and other vegetation of any quality are part of the model, I guess just good layer management. By scale I mean, if the area being modeled is large problems can occur, but usually that is more clipping than slowdown. Anything that I can learn that serves a better work flow I am interested in.