Ok, so I got a little excited about bringing Boo back. You can now
script those duration formats to your heart's content:
http://svn.gnome.org/svn/banshee/trunk/banshee/src/Extensions/Banshee.BooScript/Resources/duration-status-formats.boo
The Boo scripting is just another Banshee extension. You will need Boo
installed for this extension to build, and then it is also turned off by
default. You can enable it from the preferences dialog.