The recent places referred to is located on the folder selector in the Save/Save As... dialog.
There is a system setting for this in GlobalPreferences called NSNavRecentPlaces. You can see this from the Terminal as:
defaults find recentplaces
In Leopard and Snow Leopard, one could issue the following command to increase the recent places array -- and it would take effect immediately.
defaults write .GlobalPreferences NSNavRecentPlacesLimit -int 10
When I ran this on my 10.8.4 system, the command returned without error. Xcode showed the resource and value written in the .GlobalPreferences file, as did the above defaults find command. However, even after a reboot, there was no change. Still stuck at five recent places entries. The other notable was that the recent places locations were not changing after several Save/Save As... cycles --- deliberately to new destinations.
So, unless anyone else has additional tweaks, you may have to settle for five entries, and hopefully for you, they do change.
Here is the reference article.