Toyota Prado 2004: When does the timing chain need replacing?

We have queried a Toyota dealer and an RAC service centre about if and when we should change the timing chain/belt on our 4.0-litre V6 petrol 2004 Toyota Prado that has done 200,000 km, but neither could tell us when this should be done. They could only suggest it should be done if due or over due. We can't find reference to it in the manuals, but don't want to risk an expensive repair bill if we have missed doing it. Can you please clear this up for us? Additionally our radiator hoses have never been changed. Should this be done?