I don't believe that more than the last 8 projects can be shown. There are no options to control this in the regular user interface, and I didn't find any mechanism to increase the value from 8 in the registry. Tons of other stuff, but not that.
You might want to create shortcut links to the folders that contain the bulk of your projects in the default projects folder, to help ease navigation. That would be the quickest way to facilitate using a lot of projects.
Sorry it's not better news. Maybe you'd like to add the ability to change the MRU files numbers in the Future Features thread? (Hint, hint )