Yeah, you've picked out some of the major things that lead to looong renders, lol. The render will be long if:

the materials are complex
the rays bounce a lot (with reflections and through glass and other transparencies)
there are volumes (lights, volumetric materials, or volumetric world)
imported models have a lot of polygons
there are any special effects like soft shadows, blurred reflections, etc, or you have a higher amount of AA
the render is large
you run out of ram

basically, anything that requires your CPU to do extra calculations is going to take a while ;/

Message edited on: 02/25/2005 23:36