The guys on the GL 1800 Road Riders web page have said they are using the Iridium NGK BKR6EIX (check to virify no. is correct) and they plan to run them 100,000 miles. I assume they will put antisieze on the spark plug so they will come out of the heads at 100,000 miles.
So far, from their web page, no one has had any problems with them, but they are saying they do cost more.
I would think if they do last 100,000 miles with no problems, then throw the cost out of the window. That would be great peace of mind.
Regards,
Rosy
From NH