My 8.1 truck has been amazing. In 15yrs and 120k miles, all I've had to fix was broken manifold studs when I added headers, 2 calipers, brake lines, blower motor resistor, 1 front hub and an evap valve, and that's with 12 years of commercial snowplow use.
I'm overdue for some maintenance stuff like hoses (original) and front steering components and balljoints (original), but other than the rusted out rockers she purrs.
I've kept it cause spending $50k-$60k on a new 2500 truck just to gain 2mpg highway doesn't make sense to me.