Scanner "sleep mode" and Vuescan

I have an ancient Agfa StudioScan II flatbed (SCSI) that I've just
started using with Vuescan (Vuescan has been a lifesaver inasmuch as
there's no Agfa support for OS X with the Studioscan). In order for the
scanner to be recognized by my new Power Mac G4 (with a SCSI adapter)
it must be turned on _before_ the computer is booted. This situation
makes it likely that the scanner will be left _on_ for long periods (to
avoid frequent computer restarting); hence it's nice that this scanner
will eventually go into a sleep mode--i.e., its lightsource goes
off--after a considerable period of non-use.

My concern is that it generally seems to require a verrrry long
interval (often 5 or more hours) of non-use before the scanner realizes
that it ought to go to sleep. Is it typical for scanners to have such
a long delay before sleep mode is started? My Scanwit 2740 goes to
sleep much more "quickly" (too quickly, at times). Anyway, when I start
Vuescan and press either Preview or Scan, the StudioScan dutifully
awakens.

It would be nice (at least for _this_ scanner_) if the operator could
initiate scanner sleep. I wonder if there's the possibility--in future
versions--for Vuescan to be capable of issuing a "sleep command".

Phil