Thanks all for your replies. I managed to get more details. The front rotors apparently start at 30mm and they are considered unroadworthy at 27mm. Mine were 27.45mm hence the recommendation to change. I did lodge a customer complaint given just 30,000km. Let's just say in Lexus Customer Service style they are looking after me re the rotors. It appears that although dealers say this is 'normal' wear, that customers are not taking it further and complaining so according to head office there is no issue. Always good to let them know if you are not happy.