Addendum: I killed gpm, and let the machine run overnight. The monitor was still on and running this morning.
Gpm is definitely the culprit; seeminly, it ignores the "Put display to sleep when inactive for:" slider, and does what it wants to do (which, seemingly, puts the computer to sleep after 20 minutes of "inactivity", where "inactivity" means "not using the mouse and keyboard for anything".)
Addendum: I killed gpm, and let the machine run overnight. The monitor was still on and running this morning.
Gpm is definitely the culprit; seeminly, it ignores the "Put display to sleep when inactive for:" slider, and does what it wants to do (which, seemingly, puts the computer to sleep after 20 minutes of "inactivity", where "inactivity" means "not using the mouse and keyboard for anything".)