When the timing belt broke on my 1990 LS400 when the water pump failed at around 75,000 miles, the engine sputtered and died. I was going perhaps 35 mph and was able to coast into a convenience store parking lot. There was no damage, I had the timing belt replaced, and I drove the car for other 7 or 8 years until I sold it in 2003 when it had about 183,000 miles on it. I had the timing belt replaced for a second time at 180,000 miles. When I last spoke with the car's current owner, he said the car is at well over 250,000 miles.
I forgot the exact number of miles but a coworker of mine drove his Camry with a non-interference engine to way over 200,000 miles before the timing belt broke.
IMO, the main reason to replace a timing belt on a non-enterference engine is to keep from getting stranded and having to call a tow truck or having the engine stop in a dangerous situation. To say the least, having a timing belt break on a trip or in a remote area can be a very expensive and inconvenient proposition.
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I would like to add that I have had the timing belt replaced for my 95 Corolla at 89k and 97 Es300 at 110k. Both timing belts were in great condition and I wondered if I wasted money to replace them. Lexus dealer did not change the water pump because he inspected it and found nothing wrong with it. My mechanic on the other hand would have just changed the waterpump. Sometime it pays to go to the dealer - at least the honest ones.
My 95 corolla has 170k miles and I have not replced the timing belt again.