How often do you want to change the candles in BMW 5 E60?

According to the regulation, BMW 5 E60 candles in petrol engine need to be changed once per 100,000 km. The need to change the owner shall notify the on-board computer. However, if the symptoms of the candlelight (for example, misfiring) appear, the candles can be changed before-after 25,000-30,000 km of mileage.