My wife took in our 2010 ES350 for service today at our Lexus dealer. It has 22k miles. The service guy told her that the power steering fluid was starting to look 'dirty', and that we should consider getting it flushed within the next couple of services. We have had 2 other ES models that have hit 100k, and have never had to do this. He said it was a problem with this model. Is this for real, or just a way to help them to pay for their new service facility?