I had a 2019 BMW R1250GS. Came from factory with NGK Iridium plugs.
Discovered this at 27,000 kms and likely like this since 13,000 kms. Took the dealer till 40,000 kms to find out the bike had a faulty O2 sensor, even though i started complaining about serious detonation (and at times i think pre-ignition) at 13,000 kms and thru till 40,000 kms where i insisted thhey do every check possible to get to the root cause of the detonation. Slack, not interested workshop manager not taking ownership of the issue at 13,000 kms and finding the problem.
Plug from the other cylinder at 27,000 kms. Copper core under the Iridium tip burning away. Plug running hot.
Plug from 2020 BMW 1250GSA at 19,700 kms. Plugs still running hot and burning away under the Iridium tip.
BMW 1200 engines pre 2019 ran copper core plugs with replacement interval at 20,000 kms. At 20,000 kms the plugs came out looking like they could do another 40,000 kms.
With the 1250 engine, BMW replaced the copper core plugs with Iridium but retained the 20,000 kms replacement interval. It's likely no Iridium tips would have been attached by 30,000 kms on both the 2019 & 2020 bike.
Appears the plugs (same 8 heat range) in both the 2019 & 2020 engines are too hot and burning away.
Now running 9 heat range but will take 10,000 kms to see if this is the fix.
So much for the claimed longevity of Iridium plugs when run in BMW bike engines.