Are you sure? What did the marketing guys tell the engineers? I can imagine a conversation that went something like this, "Engineer says: We can show that running the engine at these high power levels will shorten the longevity. Marketing says: It doesn't matter, if we don't keep up with the torque race, it will badly hurt sales. Just keep turning the power up, we've calculated the number of hurt engines before the warranty ends and we will still be way ahead in profits. Just do it."
Maybe we are talking about two different issues. I'm talking about problem free longevity and you seem to be talking about catastrophic failure. We have already shown running with high EGTs will cause oil consumption and who knows what other long term issues. Borg Warner says the maximum continuous turbine inlet temperature for this turbo is 1472°F, I exceeded that by quite a bit. Not good for longevity. It can clearly be shown in UOA that if you run high EGTs the aluminum will increase per thousand miles. The aluminum is coming from the pistons, as the hotter they get, the softer they get. Not good for longevity. I choose to modify how it pull with my truck, because I'm concerned about longevity, not only for the engine, but also for the after treatment system, which is hurt by zinc, phosphorous, and ash from the consumed engine oil.
It can be argued that it's ok to run this engine at WOT and it won't blow up catastrophically and it can be argued that running it at WOT or very high power/heat levels will shorten the service life of the engine. We are both right.
Automakers don't just concern themselves with the % of engines that make it out of warranty. They are concerned with long term reliability. They also balance that against performance levels and cost.
I'm not talking about catastrophic failure. I'm talking about B10 and/or B50 reliability. Duty cycles play a large factor in this. What percentage of overall run time is spent at WOT, even when towing? The answer is, not much.
The aviation guys talking about running their turbines at reduced power is a different matter. Engines on light duty trucks and cars spend most of their operation below 30% of their maximum output. Aircraft engines only run below 30% of their max output at ground idle and perhaps descent. Climb and cruise are what, about the 75% +/- 10% range? Im sure you pilots will correct me if Im wrong. Gas turbines also have much different degradation mechanisms compared to reciprocating engines. They are primarily time-limited by thermal degradation of the hot section components. For reciprocating engines the primary wearout mechanisms are due to actual wear of mechanical components. Mainly rings, upper cylinder, valves, and con rod bearings.
You say BW lists the max continuous TIT as 1472°. The key word there is CONTINUOUS. 1515° is only 43° above their continuous limit. Turbomachinery hot sections also typically have 30, 15, 5, and/or 1 minute ratings. Not every turbo has every one of those individual ratings, but the point is that they, like the pistons and valves, can tolerate progressively higher temps for shorter periods of time. Such excursions are duty cycle limited, so as an example if the turbine has a 5 minute rating of 1600°, that is 5 minutes per hour. Id bet that 1515° is within either the 30 or 15 minute envelope. I also bet BW doesn't publish that information. They do give it to the automakers, so the engineers can maximize the engines output within those limits.
In any case, its your truck and you are free to use it how you wish. If you really want to keep EGT's down, its a single EFI Live tune away. You will lose a significant amount of peak power, but the right tune can keep your EGT's below 1200°F.
The question is, if you are trying to maximize the life of the engine, who will be the beneficiary? Do you keep your trucks for 3,4, 500k+ miles? Or are you the type of person who trades/sells it after 100 or 200k miles?