I have a file with a forest with 1000 trees and needless to say it slows down Rhino a bit. So when I need the speed I turn the layer off. But then I realized that if I only turn off the layer that the block parts are on, and not the layer that the blocks them self are on, then things doesn’t speed up. Even though the scene appears empty and there is nothing to select.
(They layer with the blocks are on and the layer whit the block parts is off.)
So apparently Rhino calculates where all those parts are even though it “knows” that they are not visible. I imagine handling the “what parts are visible” prior to handling the blocks would speed up Rhino quite a bit regarding blocks in V6.
I’ll send a file if you need to check it out your self.