It really depends on the engine in question. On a ford 302 Gasser, then by all means YES. I would never consider running egts like that extended.
But the fact of the matter is, that most commercially available diesel engines intended for durated use include piston dome cooling jets from the factory.
International Navistar (the maker of my powerstroke) specifies a durated Pre-turbo egt maximum of 1250 degrees. This is straight from the maker of the engine with the assumed saftey factors in place. This is the temperature at which they feel the engine will still run to its intended service life at full power without injury to pistons, valves, seats and so on.
The 6BT is rated to over 1300 degrees egt durated by cummins.
These engines are designed to shed piston and valve heat and have cooling systems dedicated to those tasks.
You don't usually see piston failure in a powerstroke until you start towing down the interstate running 1350-1400+ degrees sustained. And even then, it's more of a slow wearing out process. You really need 1500-1700 sustained to actually blow a hole in a piston like a torch on one.
I think these light diesels are tougher than they might be given credit for right now.
And this isn't just something I read out of a book. I have seen tons, and tons, and tons of failures with these powerstrokes, from ring lands cracked by nitrous, domes cracked in half from cyinder pressure spikes, cylinder walls blown open into the water passages, rods horseshoed around until the wristpin hits the big end, entire blocks ripped in half dumping the crank through the oilpan, pistons with holes that look like you hit them with the torch, bent, broken and mangled rockers/pushrods/valves from piston:valve contact through drive/boost pressure, so many head gaskets failures from stock to copper, to multilayer, to o-ringed, to fire-ringed, yada yada yada.........
I know where these engines fail all too well, and 1200 degrees egt is a joke. It's actually still 50 degrees below the OEM spec, lol. And the B series cummins is actually rated even higher than that (stock).
I'm somewhat against the grain on the coatings, but my personal opinion is, if you have even a shred of efficiency in your turbo design, you do not need any coatings to survive. I've seen engines with some coated and some uncoated pistons (due to running out of time). It was in a pulling truck running OVER 2000 degrees egt and the pistons that cracked in half were the coated, lol. Not that the coating explicitly caused it, but in a situation like that you just can't help but laugh at coating parts.
The point is just that, coating is a worthless expense on one of these engines not exceeding 1300 or so sustained. Because the engine is probably OEM spec'ed to run that temp from the factory sustained, 24-7 anyway.