If you are willing to do a bit more modeling, you can reduce file size by using components for objects that repeat in your model. You can save even more space by reducing the number of sides that you generate with the circle tool when you create a circle. This is especially helpful if you plan on using a Push/Pull or Follow Me tool, as it will reduce the number of faces created later on. Finally you can save on space by only importing what you need from the 3D Warehouse. There are many highly detailed quality models on the warehouse, sometimes you do not need all the details that a component comes with. Do not be afraid to strip out excess detail you do not need.