When a timing belt breaks, it will cause catastrophic engine damage. Tming belts should be replaced at the specified mileage interval. This mileage can vary greatly from one vehicle to an other. This is a “critical” service for timing belt equipped vehicles. Timing belt service can also vary greatly in cost from vehicle to vehicle.
All though there is no set time limit on timing belts it is always a good idea every few years to have it inspected. In this area, we live in a very dry climate that can be very ruff on rubber like timing belts.