It might be wise to collect all of your saved assets - whether they be 3DS models, FBX files, Revit files, whatever - to some assets folder that is separate from an Unreal folder structure. Same goes for materials. Bonus points if you organize your files with screenshots and previews.
If you’re going to reuse files over and over, I’d suggest not pulling them into a project until you know you need them. Otherwise, you’re wasting space (and load time.)