Feedback on size of Class Diagrams

I would like to get feedback on the typical number of shapes you have in a class diagram – is it 10, 25, 50, 100 that you’ll be actively using?  The reason for this is that we want to optimize the performance for a typical class diagram while you are in active development (as opposed to diagrams that are created for documentation purpose).

My personal preference is to have a diagram of not more than 10-15 shapes that represents the classes I am currently working on.  Of course when I want to visualize an existing project, I may want to look at most if not all of the classes in one diagram and see how they are related.  But I will just use that as a reference and not the diagram I am actively working on.