Babying a diesel engine

[Fore and Aft]

As a marine surveyor I go on a lot of sea trials and I often hear owners say they do not push their Diesel engine beyond a certain rpm. I used to be in the same mindset thinking that the lower rpm will help the engine live longer?
But for years I have been observing trucks, earth moving equipment and even my Kia diesel car (320,000km). These engines all still last a long time despite being flogged fairly hard. So is it really going to make a difference to my engine life if I run my Yanmar 2GMF at 2000 or 3000 rpm?
Cheers