Valve lash mileage?

[DickWells]

Got 182 K miles on the Sierra, now, and have been thinking about getting at the valve lash adjustment. Looked through the Helm manuals and the diesel engine 6.6 supplement to the owner's manual, and neither one has anything to say about the adjustment interval. So, I'm asking the experts on TDP.

While my engine has always been a little less "solid" sounding than my son's 03 Chevy Dually, it's not particularly noisy, even though it has 80 K more miles than his. Am I just being paranoid, or am I getting into the to-do time and mileage area?

Thanks, DW