The problem with timing belts is that they often fail with little or no visible signs of wear. Timing belts often suffer catastrophic failures seemingly out of the blue when they're past the "expiration date." However, the OEM belt is very, very durable and should still have some life left, even after 16 years and 57k. With that said, you may want to change it at 60k just as preventative maintenance because 16 years is a long time for a rubber belt in general. On the other hand, your engine is non-interference, so you could conceivable use your existing belt until it snaps, which may or may not be in the near future. More likely than not, it will be several years or tens of thousands of miles from now for that situation to arise. In other words, if you're willing to risk it, you can put off the timing belt indefinitely, keeping in mind that it may leave you stranded one day in the distant or not-so-distant future.