Since when is it uncommon for a OM617 cylinder to crack?

I have two in my possession (one of these days I'll get around to stripping them out and junking them) which have cracks in the combustion chamber areas. I have replaced probably 15 or 20 OM617 cylinder heads over the years. Over-heating is the cause.

There a few threads here on the board covering this very circumstance.

'85 300TDT, Just pulled my Head, need some encouragement

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now