From what I've seen, 6.4 trucks that get worked hard and driven on the highway lots seem to last just fine. Seen a few that are way up there in mileage, no major problems.
It's the trucks that people use as personal chariots to cruise around town, and galavant. usually develop major issues from the emissions junk.

 

What's the average you've seen on high mileage 6.4's?

I periodically check the private market and can only find trucks with ~250,000. I saw ONE recovery truck with 400,000 but Oasis said it had two or three fuel pumps, radiators, and a TON of repairs.

 

That sounds about normal, from what I've seen. The 6.4 pumps last about 200,000 to 300,000 km's, but on the bright side, usually it's just the pump that needs replacing. This isn't a bad thing, chev 6.5 diesels don't make it that long, and the pumps aren't much cheaper.
Mechanical pumps don't last longer, they just keep running when they fall way out of spec, thats my opinion.

 

Would it be almost safe to say that the fuel pump might be a "wear and tear" item and one may consider replacing the pump at say.... 200,000-250,000 miles as preventative maintenance?

 

I would say that's pretty reasonable, I wonder what they see as far as durability on the Maxxforce7, basically the same motor.

 

I don't know about that, they could go longer or fail sooner. The real delimna is that when it craps the bed, you have an undrivable truck, where older engines would just run rough.

 

Same issue as the ford version, oil dilution.
Overall, the 6.4 / maxxforce 7 is an awesome motor, but the emission system is hard on it.