A couple of thoughts...
You could use display states to do what Anna is suggesting. You could also create a simplified configuration of parts that have a significant number of surfaces (such as a part with a high number of patterned features). You would then use the simplified configuration of the part in the assemblies where they are used. This would lessen the number of surfaces shown in your assembly model and relieve your computer from the burden of rendering and updating all those surfaces. If you have SolidWorks Professional, or if you have access to the SolidWorks Utilities add-in, then there is a tool that helps with geometry simplification for cases such as these. It will build a configuration in your part file(s) and de-feature your part automatically where it can to simplify the geometry. You can do this at the assembly level and have SolidWorks create simplified configurations in the part files. This would do the bulk of the work. You could then go into each part file and change how parts are simplified or strip away even more features to simplify the config at the part level. Don't know if this applies to your situation, but thought I would mention, as round-tripping parts breaks the associativity to the real part file that defines the geometry. If creating a simplified config could help, then you might not need to round trip.
Pete