Copitor is a very sensible script,   allows you to copy all objects from a scene in the scene on a simple principle of copy-paste. You can copy multiple objects in parallel. The copied objects do not spend memory because it is temporarily stored on disk. But don't forget to copy the textures folder to the place of residence of the new project, otherwise the objects are copied, but textures are not to be. Like most of the scripts is free and is suitable for all modern versions of 3ds max.