I own several dodge cummins trucks... and a couple of fords... we've never done it.....
00 F550 with 350 K miles... . 04 3500 Dually with 192K miles etc.....
But... . I've seen a huge difference on gasoline vehicles... . and do it on my stuff every 18 months or so... . (gas cars) the chemicals used flush out the varnish that gasoline is know to cause.....
We do service the fuel filters on time with a quality filter... .