The main problem with the earlier E series was the bolts stretching, this would then cause the head to bounce resulting in blown head gaskets and so on. the AU metal shim gaskets are more resiliant to blowing along with better head bolts has almost stopped the problem of blowing out gaskets.

Fair enough - that makes sense - but certainly at least in the case of my car, being torqued up absolutely dry wouldn't have helped either (my bolts were certainly not stretched - they're still working fine after 12 years and being reused 3 times).

As I've said - using the correct values PLUS performing the torquing procedure properly is critical.

That may explain why they have been used 3 times in 12 years, they may have to be renewed so thay last for say 10 years.