For the 6430u (and I suspect related family) I had a hard time locating info on how to control the timeout. Chat support was helpful but didn't have exact info. I have provided that to them so one would hope not too many of you need to read this post. :) .

You need the Feature Enhancement Pack (FEP) (Control Point has been superceded by FEP)
Go to C:\Program Files\Dell\Feature Enhancement Pack (default location for Feature Enhancement Pack installation).

Readme file provides the details (use Control Panel) as indicated here:

In the Windows Control Panel - Keyboard related tabs:
        - Dell Keyboard Hotkey Settings - Lists system function keys.
        - Dell Keyboard Backlight Settings - Provides control for keyboard
          backlighting (only on computers that support backlighting).
        - Dell Battery Information - Provides information about the
          batteries installed in your computer

Control Panel > Hardware and Sound:

Change as desired (60 sec timeout here: