between 80,000 and 100,000 kilometers is the appropriate time to replace your timing belt and other related parts.

What I normally do, I visually check my timing belt, especially now that I'm hitting 70K, for signs of cracks and other abnormal appearance that would indicate that it's time for replacement.

Visually check your T-Belt and below are the tell tale signs of a T-Belt due for replacement (got this from the net)

1. Hardened backing rubber (the rubber appears glossy and non-elastic. If you scratch it with your fingernails, it will not leave any mark, this means it's time for replacement)

2. Surface cracks on the backing rubber

3. Cracks on the tooth bottom or missing teeth.

4. Cracks on the belt sides or abnormal wear on the belt sides. Note: The sides of the T-Belt are normal if they are sharp as if they were cut by a sharp knife.

HTH