a PCB has 3000 components , how to make lighter for MCAD import

I have to import a PCB with almost 3000 components, and working for a project often i have to have 4-5 different baords , each with 2500-300 parts ( from MCAD library depicting electrical parts) , and on top of that the mechanical parts to design full assembly.

how can i make the PCB assemblies with all components lighter so when viewing/moving/zoom in, zoom out, pan, etc can be faster. 

for boards with 200-500 pcs, i can make iges ( an loose all ref des, etc) and assemble in my assemblies is ok.

but with 3000 parts, even the iges file is big and takes memory to import etc.

any  new ideas.