Here is another one-size-fits-all maintenance schedule which makes no sense. By the time my car hits 105K(city) miles, it will be 12 to 15 years old, and my timing belt, if still intact, will have been through far more than average stress. My personal recommendation is about 7 years or 105K mostly highway miles or 60K mostly urban miles, whichever of the above comes first.
Disclosure: I got a very premature timing belt changeout (4 years, 25K miles) at half price, because it was in conjunction with cam seal and cam chain adjuster replacement. Barring other problems with the engine, I plan to replace this new timing belt in 6 or 7 years, per my recommendation, above.