At what mileage point should the timing chain be replaced in 1985 300SD

The timing chain has o recommended change interval, regular engine oil changes keep things in good order. I don't "see summary", it is not displayed. If you think there is a timing chain problem with your car, call an independent Mercedes shop or dealer in your area and ask them in there experience do they see a problem with the timing chain on these engines or would the recommend changing the chain before a certain mileage.