After a fresh install of Ubuntu 12.10, my screen still goes off after about ten minutes. I've been to the Brightness and Lock control panel. The
Turn screen off when inactive for: setting is set to
I've been through the
dconf editor searching for
idle changing parameters. This doesn't seem to have any effect on the display timeout.
Here's one more interesting thing, the screen doesn't go off, it just goes black. The back lighting is still on, and all the pixels are black.
When it goes black, it does a very pleasant quick dim to black.
Similarly, it quickly un-dim's after a key press, mouse movement, or mouse click.