I'm not sure that there are enough useable facts in this thread to be worth reading again.

The cause of the cracking has never been determined,
The life expectancy of any head isn't predictable,
No preventative measure has shown to be effective nor ineffective.

There are many #14 heads running around with 1/4million miles on them and no operating issues, including the one on my spare engine. I might someday pull the head from that engine and "freshen" the engine, but all of the upper-hose tests and gas-in-coolant tests have shown it and the one on my runner to be good, which might only mean that they don't have cracks large enough to be detectable. Other manufacturers' heads mentioned here have allowable cracks.

The percentage of heads that have failed is apparently small, but I haven't seen a poll. Polls typically lie anyway because it is more likely you will post to a poll if you have had a failure than if you haven't.

There were changes/redesigns to the head, but not necessarily for head cracking issues. Also, some of these head casting numbers (#15 for example) are for non-turbo engines, one reason we don't see them in the US. There are redesigns, sometimes for efficiency, for noise level, for emissions, for increased power (3.5l for example),for ease of casting, to save metal, ... any ideas about why the head was redesigned is purely speculation at this point.

Any member ever find the guy that sells the replacement aftermarket spanish heads? About 800.00 if I remember. Too bad he is not also a member here.
May do no harm to always use a wetter agent in engines with those heads as well.

The 14 in the SDL with the original known to be weak head gasket is still doing just fine. At this point it could probably stand a valve job so if the head goes it wouldn't be so bad.

At 267k miles I wonder how worn the valves are?

Recycled
 

for new member education on this common issue.