The ignition coils should regularly maintain and clean rather than replacement. Check them every 20,000 miles, and replace them when they are senescent. The high performance ignition coil is importanct for reducing carbon deposit of engine, prolonging engine life-span etc. u will find them from http://www.maxspeedingrods.co.uk/ignitio...

Only when it fails. It is too expensive to replace every component of the car to prevent breakdowns.

No most will go for the life of the car, it is not normally a maintenance item.

No. They only need replaced when they fail.

yes , every 20 years without fail

Well, maybe every 100,000 miles or so.(when you do an engine rebuild)