I cannot believe I use Fedora with the default ten seconds screen dimming for almost two years now. When running on battery, this is very annoying. I need to think more than 10 seconds during coding, and this is driving me crazy.
So I found a nice little post about this and sharing. To determine your value just run:
$ gsettings get org.gnome.settings-daemon.plugins.power idle-dim-time 10
To set it to lets say reasonable thirty seconds, just do this:
$ gsettings set org.gnome.settings-daemon.plugins.power idle-dim-time 30