A few weeks back, I posted a question on this, as my truck now has 182 K on it.
Got no responses, and went back through my books to try and pinpoint a scheduled valve adjustment interval, with no info found. So, last week, I stopped in at the local Chevy dealer and asked the same question at the service desk. The manager had never heard the question, so he went to one of his three diesel men. The mechanic has over 15 years with this dealer, and has never done a Dura Max in the 14 years that they've been on the market. So, I guess I have my answer. If my DM isn't clattering like crazy, then I guess I'd better stop fretting about it and go on my merry way.