Hi,
It would be good, for large scenes, especially for high-poly models, to have a simplified model in the viewport. For instance a box (shaded or wired) would be good.
This has nothing to do with the distance, just for better handling in the viewport.
Only the rendering does show the high poly.
Second is, to include or exclude a model from reflection and refraction.
Third is, to give a geometry more or less GI.
Thank you!