2 Answers
- Open the dconf-editor.
- Find org.gnome.settings-daemon.plugins.media-keys in the tree of settings.
- Find the setting named max-screencast-length (the default value is 30 seconds)
- Change it to 600 seconds for 10 minutes (10 * 60 seconds), or 1800 seconds for 30 minutes (30 * 60 seconds)