How do I export a complicated floorplan and ductwork from CAD to Adobe Illustrator in vector format (without freezing/crashing Illustrator)?

I've tried lowering the quality of the plot in CAD but that makes the curves so bad it's unusable. Every time I try and open the exported file in Illustrator it takes forever and if/when it loads if I click anywhere on the screen it takes forever to process. Each edit on the document takes 20 to 30 minutes at least.