What's the largest you would want an interior cell to be? Is it determined really by the cell and its architecture, or is it a question of objects and/or actors in the cell?

At what point would you look at a dungeon, and say "That's a little too large to be one cell. I need to break that into two cells."

Actually I've heard there's also a limit about the number of objects (not just items) you can place in a single interior......but others know better than me, about this topic.