G'day all, I will admit that I change my plugs when I check the valve clearances, at about 24-25,000 Klicks.
I use the common or garden non iridium cheap arse charlie NGK plugs and when they come out I reckon they would quite easily go again.
I also don't encounter any drop off of performance or fuel economy just before a plug change, or improvement after.
If I was facing the expense or inconvenience of changing every 7,500 Klicks I would 100% not bother.
However if you want to change your iridium plugs at 7,500 can I have the old ones please?