Here is an interesting one;
One of my users drawings was originally created around 2006+/-, it has about 100+/- layout tabs in it.
He has since then used it in Civil3D 2012 and it performs very poorly when he changes layout tabs, bringing up the plot dialogue box, and opening in general. He has tried to save it to 2012 format and nothing improves. The one thing that does work is if he blocks everything out into a new drawing; but after a period of time it starts to do the same again.
Any thoughts on what might cause this, sounds like some sort of cache issue?
100+ Layout tabs? I'm surprised it "performs" at all. The max tabs we find for performance of our roadway designs is 10. Sure, it may not be the ultimate performance breakover point, but it works for us. Just try creating a file with a saveas then eliminating most of the layouts. See if that changes things.
I agree, no way I would even attempt to work with 100 Layout tabs.
You can try unchecking Maintain Visual Fidelity in your Options (as long as you won't be saving the file down to an earlier version). This helps performance usually. It checks for annotative objects (even if you don't have any) everytime you plot, switch tabs, regen, etc. It can be a killer on a drawing with just a couple tabs.