If your models rotate slowly try the following
Reduce surround lights, because they can slow down rendering
Try to reduce number of different materials in the external 3D editor
Make sure textures is not too large 1024 or lower is recommended
Optimize your model under external editor, like ProOptimizer in 3DS Max
See the article for reducing polygons here
https://www.shapeways.com/tutorials/polygon_reduction_with_meshlab