I drove a commercial tractor trailer for 25+ years. 90% Macks. The early years w/U models, the bulk with CH/Vision's using strangled EM7-250 or 315s. In all those years, with many dozens of co-workers, I only -heard- of one internal engine failure. Some new guy managed to grossly overspeed his CH's engine (pretty hard to do- I'd guess going down a hill). 3 or 4 pushrods failed. I was told the ends fell out. I saw my pal have one catastrophic turbo failure in 86' then in the mid 2000 there were many turbo failures with the new variable nozzle units. None of these hurt the engine. I had one myself around 06. After the Co turned my 315 down I had compressor surge. Told 2 different shop dudes, neither knew what I was talking about. The senior mechanic said 'they don't have variable nozzle turbos'. I remember walking over to one someone was working on (his?) and showed him the servo and linkage. These engines were designed to have it all in at 1100rpm (called high torque rise, 1000 was where it started to happen), and be all done at 1800. No load was 2000. Warning on the visors said 2100. They way the company had the computer /gearing arranged 1500-1600 was all you would get in top gear. 1200 was torque peak. These low speed was great for ring life and fuel economy. Turbo and aftercooling made all this happen. Long stroke helped too. Longer than the MF. BTW output was supposed to be 1000-1400 lb-ft, fuel economy was about 9mpg highway. It was designed this way and worked well (well, until Renault appeared, lol). The MF would seems, to be designed differently, for different usage, and different life span, as Chuck points out.
Guys that wrench know and see it all, a few of whom are around here. They have been quiet. I'll bet they are too busy, either working, or laughing.