How often do you change a subaru timing belt?

About every 60,000 miles. For the 1999 and earlier models, the oil pump typically starts to leak around 100,000 miles. The leaking oil contaminates the timing belt and water pump. It is best to have all three items repaired at the same time. Cost is usually $900-1200 and can be done in one day by a reputable shop. Also you should get your hoses changed at the same time to make sure you don't get leaks