Radiator flushes should be carried out at least once every two years or every 30,000 km as preventative maintenance.
The inhibitor in your radiator system has three roles. First to raise the boiling point and lower the freezing point. Secondly to prevent corrosion and electrolysis. Thirdly to tell the 'ECU' that your temperature is correct, thus saving fuel.
Your car's radiator needs to be clean to be cool.
As time goes on, your inhibitor breaks down, your car's radiator builds up solid deposits that can clog the cooling system and damage can be done to your aluminium components, such as your water pump
A quick, inexpensive radiator flush can keep the system in shape.