According to the service manual workshop manual:
The condition of camshaft drive belts should always be
checked on vehicles which have more than 50,000 miles. Although some
manufacturers do not recommend belt replacement at a specified
mileage, others require it at 60,000-100,000 miles.
Replace the timing belt every 72 months or 60,000 miles if
the vehicle is operated under Severe Service conditions such as
frequent idling or extensive long distance driving at low speeds.
It also says in the toyota manual to charge 1.8 - 2.3 hours for cambelt change
hope this helps