Was told by Toyota when I picked my Prado up from a service, that they have been told to replace the seals when doing Routine valve Clearance......I think every 40,000k's. Don't hold me to the k's I will need to check that out. The dealers were also told not to scrimp on the services........I think some dealers were doing this. I asked him about if he knew of any guards that have been cracking on the 150, he said never heard of it through their dealership........I think they are well aware of the cracking on the 120's. He also admitted that they had a lot of problems with the old copper seals........