Anyone with an engineering background knows that if you increase output reliability and longevity go down.
Theoretically, yes, if you increase (and use) max output. But if you drive by the gauges and never allow more than 1,250° pre-turbo exhaust gas temp (EGT) or 25 PSI turbo boost, there is no reason for increased wear and tear on the engine when towing or hauling, compared to what it was designed to produce.
We're not talking about producing more power at the 2,600 RPM peak of the RPM/horsepower curve, but down around 1,800 to 2,000 RPM where you need it it for climbing slight grades at highway speeds without the 4R100 tranny downshifting out of overdrive. At that RPM, the tuned engine is not producing all the horses it was designed to produce at the peak of the HP curve, but a lot more than it would produce at that same RPM with the stock tune.
The following chart is hard to read, but it shows the HP and torque curves of the 2001 7.3L engine. Notice it has 250 horses at 2,600 RPM, but only about 190 horses at 2,000 RPM while maintaining torque at almost 500 lb/ft. So if you pump up the horses at 2,000 RPM by 20 percent, you'll have about 230 horses along with about 500 lb/ft of torque - still less than the peak power of the stock engine.
Therefore, no increased wear and tear compared to winding the engine up to its stock peak output.
Ford engineers say my engine has a life expentancy of 250,000 miles given "normal" maintenance, care, and driving. But my engine gets excellent maintenance and is never allowed to get too hot or produce too much turbo boost, so I expect around 400,000 miles out of it before it needs any sort of overhaul.
Granted, when using all the 60 extra horses of a 60-tow tune for mountain climbing, you''ll be using more than the max of 250 stock horses. That's when you have to use your gauges and never allow more than the red lines for EGT or boost. The pre-turbo EGT redline of 1,250° means you can't use all 310 horses for more than a few moments, then you have to back out of the go pedal and maintain between 1,200° and 1,250° until you top out at the top of the pass.
So in that case of using all 310 horses to force the 14,000-pound motorhome up the mountain while downshifted and running at 2,600 to over 3,000 RPM, you'll probably slightly reduce the total life of the engine, but not by a significant amount if you drive by the gauges. But using more than the stock 250 horses for more than a few moments each time should be for only a tiny percentage of the total miles on the engine.
Granted, if you're an idjit that insists on pedal to the metal all the way to the top of the pass and to heck with the gauges, then your hot-rodded engine won't be long for this world.