In fact my numbers may be wrong, but for the cost of the part I do not see the need to leave it so long, that piece of the picture was not in very good condition and were only 30.000 km ...

In my case to do a tune up, is what I do change the copper every 10,000 km
the iridium each 20.000, 40.000 know that last, but it also revised the state of combustion, according to the last iridium 100.000 km, but these data as long as the car is stock, I think to move a parameter continually need to be revised ...

cost-benefit in order to see the problem not to do before, such as a synthetic oil last say 20,000 km, but the oil filter not as bad a thing as the other, then a filter every 10,000 stock ...

In my case I change it every 10,000 km although it is synthetic, but does not benefit me much, I think it helps me more to leave it up to 20.000 km, for which the filter is changed every 5,000 km, I think the benefit is that the injury, and cost is not representative ...

Our gasoline is not the same quality and our streets are worse than you, so I have more care ...