I've talked to toyota mechanics that have been in the business for over 20 years, and they replaced blown head gaskets with the car under warrantee less than 30k miles!
The engines fail because they have design flaws. Toyota is not only automobile manufacturer that is immune to engineering shortcomings.
I was still replacing short blocks and cylindar heads on 3vz-e trucks that were over 10 years old under toyota's campaign VO6 recall! Mainly due to block errosion and BHGs. A 7mgte will do exactlly the same thing. Yet these two engines are the only ones I have ever seen do this.
Compared to other high performance toyota engines that ever exported to the US the 7mgte has to be the worst.