Does Blender take more time to render with extra objects that aren't visible? I've got an obj file from a client that has about 4000+ layers (individual screws etc).  There are several components that are inside of the structure, hidden from view, and I am wondering if deleting those objects will help render times.  Basically: does the renderer sample all of the polygons or only the ones visible in each frame of animation?
I had rendered an interior, I had a carpet that it used a lot of memory. Even if I rendered a part of the interior without the carpet inside the frame, the render time was big. I just had disabled the render option from outliner (you can find it in filters) and the render time has reduced.