Comment 7 for bug 1507983

John, I think the greeter just inherits whatever screen blanking settings the X server started with (and I'm not sure how to change that).

I created a shell script with "xset s 60" in it and set the "greeter-setup-script" option in lightdm.conf to point to that script. That seemed to blank the screen after 60 seconds on the main login screen.