Everyone needs some help with large models from time to time.  Here is Le Corbusier’s advice on keeping your model size down.  To the advice is to “purge all” by going under Window -> Model Info -> Statistics -> Purge Unused.  It should eliminate extra layers, styles, materials, and components that are not being used in the model.  Also, using 2D components can keep the file size down.  One can always swap out 2D components for 3D ones when the project nears completion or for rendering purposes.