a standard spark plug should last 10-20K KM...those better/performance type should last 30-50KM....
Spark plug is wear and tear part...
Also life span of spark plug depend on your engine condition...if your engine makan engine oil / wrong tuning then your spark plug will wear out faster.
anyone one know where the location of the iginition Coil which connected to distributor? mind to tell me? cos me wanna to 'pasang' tachometer.. just the sensor wire din connect to it... thx alot...