Hi, I suprised no one has responded to this yet so I'll give it a try. Simply put, the more polygons in a scene, the longer it will take to render. I favor spline models to vertex when it makes sense to use spline models because they are handled more easliy by Carrara. They also produce much smaller file sizes. Using duplicates v.s. creating new is more efficient too. The big animation time savings comes from hiding/suppressing anything that is "off camera" Additionally, lights that have effects added like Light Cone etc. should have those effects turned off in the timeline as soon as they are off camera. If you still need one of the off camera lights to illuminated the scene, they can be left "on" with only the effects suppressed. The render time savings will be hours, not minutes. Hope that this helps.