They can have issues with the injector pump if you don't run a good lube in the fuel. I have a 2002 I run power service with every fill up, no problems with mine 140k on mine. And they need a good lift pump to help cool the injector pump.
I had 260,000 on my na 6.5 GM in my tool truck. A quart of atf every other tank or so works well to keep the old mechanical pumps and injectors lubed and running smooth.
