LaserWriter 12/640 PS: Cannot change sleep mode timing

I have noticed that my LaserWriter 12/640 PS printer powers itself down into a sleep mode after every print job. It occurs about 5-10 seconds after the job finishes. I would like to change that. The LaserWriter Printer Utility software does not allow me to change the "sleep setting" on my LaserWriter 12/640 PS. I am able to change it on other Apple laser printers; how can I change the sleep setting on my LaserWriter 12/640 PS?
The LaserWriter 12/640 PS engine (the fuser, scanner and other internal parts, not including the main controller board) goes to sleep 10 seconds after the completion of a job. This is a low-level sleep feature and is a built-in, static characteristic of that print engine. It cannot be changed by the Apple Printer Utility or by downloading PostScript code.

Note: The LaserWriter 12/640 PS is Energy Star compliant and is registered with the US Environmental Protection Agency (EPA) as such.
Published Date: Feb 20, 2012