UnitSetter (free Plugin)
UnitSetter is an Object plugin that will set cinema's unit settings to the value specified in the plugin object.
This way your unit settings will be restored when you load a scene with the UnitSetter object in it, so that you dont have to change the settings yourself each time.
This will also prevent you from accidentally using wrong unit settings when switching between scenes with different settings, should you forget to adjust the cinema preferences.
If you use Cinema4D R12, this plugin is not neccessary anymore, because units are saved into the document now.
Units will not get set if the cinema preferences dialog is opened at the same time.