Hi, I own a 2006 RX400h with about 60K on it. Everything works well and I have never had problems with the batteries under the rear seat. I have read that they can cost $3-4,000 if they go out. Has anyone had to replace them yet? I love the way my unit rides and shifts (or doesn't) but would consider trading the unit in, if it would mean that much added expense in the future. Thanks in advance for any facts or opinions.