How clean is the engine looking inside? Have you check the inside of the PCV hoses to see if it has crusties or mayonnaise or just decent looking film of oil? I ask because I think what will limit your OCI is the oil’s ability to keep the engine clean rather than too low TBN or too high wear metals.
I am the orig owner. This is the longest oci i have ever went. Usually stay in the 5k-6k range. The car is also garage kept so i doubt there is corrosion from moisture. Engine is literally spotless inside. Although it has developed a slight lifter tick when cold sometimes, within the last few thousand miles, which is common of this year before the technical update.
Very clean! If you do longer OCIs than you used to, just keep an eye on the cleanliness in there. The good thing is that it is so quick and easy to do and costs you no money.