I saw a recipe for sourdough pancakes on King Arthur's website, and it called for two cups of liquid starter.  I have about 1/4 cup left over when I refresh my firm Maggie Glezer starter, but nothing like two cups!  I did make half a recipe of the pancakes and they turned out OK (they also called for baking soda, so that was safe, I guess.)  

How does going from firm starter to liquid starter go?  Two cups sounds like an awful lot!