I asked a local dealer about the T-belt given that I am close to the recommended 90K replacement mark. The dealer said officially he had to say it should be replaced at 90k. Then he went on to say he has not seen a T-belt go out on a LS430 even when not replaced with much higher mileage. I'm in SoCal so the weather is mild here; not too hot or too cold. That probably helps. I'm inclined to go beyond the 90K until some other work in needed to do it all at once. Then again, the engine is an interference engine so if your T-belt goes out it will thrash your engine with the cylinders hitting the valves. I'll probably do it some time before 120K.