It is in the WebUI Configuration page under the Maintenance tab (at the top), in the "LCD Display" menu(an idiocy by D-Link I'm afraid... as this makes it a "Liquid Crystal Display Display").
I'm hoping the new firmware will allow for the screen to remain on permanently, and that it rotates between the three display screens with an option to modify the frequency, if not, it will be on my list of feature requests for a future release