When I bought my 7.3L in 2000, I had the feeling that it would be my last truck, so I wanted it to last. The "race" for me isn't uphill, it is "time in service" with the fewest dollars spent over the longest period of time possible.
At minimum, a truck has to hold up for 15 years. For example, my previous truck was a 1979 F-250 with an anemic 400, and my first truck prior to that was a 1963 F-100 with a strong 289 and three on the tree.
Now that 15 years has passed on my current 7.3L, and now that the past 15 years has shown how expensive and complex the problems are with the newer motors that have superseded it, I think another 15 years of service from 7.3L is not only easily doable, but is the most rock solid reliable choice.
Finding a well cared for 7.3L with only 75,000 miles that hasn't been mucked with in terms of modifications like tunes, chips, injectors, etc is a good find that I wouldn't pass up if I didn't have one already.