Ang difference ra man siguro sa iridium and plain copper NGK sparkplugs are iridium last longer. But then it costs eight times as much than cheap copper sparkplugs. But even if it is claimed to last a long time, the manufacturers still recommend changing sparkplugs every 30,000 kilometers because firing points tend to wear off.
I drive a decade civic and it still runs good after changing the sparkplugs with cheap OEM coppers.