Thanks for the pointer to the tomshardware post. It referred to a freeware program called HDDscan (written by Artem Rubtsov)
The author of the post said it did NOT work for him
...however, it DOES work for me. This may be because my individual drives support the feature. See below.
I was very surprised that I wasn't already aware of HDDscan.
I'll try it for awhile and see how things go.
In some very quick and simple tests, HDDscan DOES seem to provide for BOTH individual drive
timed spin-down control AND manual spin-down control (although the manual "spin-down now" is not the single-button click like I was looking for...you'd have to keep HDDscan running all the time and actively displaying the "Features" panel to do that).
However, for these to work, the target drive must
support the "Power Management" feature. For example, in my test machine I have an ~5 year-old 250GB Western Digital drive. It apparently does NOT support either power management option as I can't even access the Features "tab" in HDDscan...it's grayed-out...the only drive on which that happens. The test machine has a mix of SATA and PATA Samsung, Hitachi, Maxtor, Seagate, Western Digital drives from 40GB to 2TB.
Click on "Identity Info" then look at the "Power Management" parm and it must show "Supported". It apparently does not require that the drive support "Advanced Power Management". I've got a Seagate SATA drive and a Samsung SATA drive. They both support "Power Management" but the Seagate drive does NOT support "APM" but does support "Power Management". Both the Samsung and Seagate drives respond as expected to both the time and manual spin-down controls.
You go to the "Features" option, then click on "IDE Features", set your time interval (0secs to 12hours) or click on the "Spindown (now)" button as desired.
I also point out that AHCI is NOT enabled on my SATA drives (not set as removable/swappable). I don't know if HDDscan would work on AHCI enabled drives (in addition to his drives possibly not supporting "Power Management", if his AHCI was enabled could
be another reason the tomshardware post guy's attempt didn't work).