I don't know why people keep saying to change plugs every year or 100 hours. That is not a requirement, it's the "check and inspect" interval per the owner's manual. You inspect them at 100 hours or once a year and if worn, you replace them. If they're good, re-install and check them again next interval period.
For us in the north, yearly use is 30-50 hours - so change them every 30 hours or so? That's just a waste of money and material (LFR6A plugs are $8.20 + tax = $75 a set up here). One of my factory original plugs that are 3 years old I just pulled at 201 hours is below. It gaps at about 0.86mm which is within spec, heat range, colour and condition are all perfect, and engines are purring nicely with 53mph top speed...no reason to change them for maybe another 100 hours (click to enlarge):
View attachment 201351
However I changed them with new plugs yesterday to do comparisons of old vs new, and then kept a set for spares. I check them every season and should be good for 4 years or more now which makes the cost about $18.75 / year which is more reasonable. It's not the cost that bothers me, it's the wasteful nature of tossing away perfectly good plugs. Same goes for oil changes where stealerships want to change synthetic oil every 5k - it's a complete waste of materials.
