I have noticed that my monitor may stay on long after the time limit
set in Control Panel/Power Options. This usually happens after I retire
for the night. I have determined that the only time it happens is when I
place my Logitech Lasermouse in its charging cradle,... if I leave the
mouse on the pad, the monitor shuts down, if I place the mouse in the
charging cradle, the monitor stays on. I have no idea whether there is a
fix for this.