I'm at 185,000 miles with my 2000 RX 300 on the original timing belt. However, I have a slow oil seal leak and I was told to wait to change the belt until around 200,000 miles and do all the seals and the belt at the same time. Like you, I have serviced it religiously every 5000 miles at the Dealer until the last 20,000 miles when I switched to every 5000 miles at a local garage who only works on Japanese cars (for half the price). She still runs like a charm