IMO tbn numbers don't mean much. I've had Blackstone recommend I go further when the tbn was already down to 1.0
Blackstone are the only people who make that kind of recommendation. PQIA feel that oil should be changed when TBN is 3 and all other oil labs are in that same range.
I look more at the wear numbers and the viscocity.
I agree that viscosity is important because rising viscosity means the oil is oxidizing. Remember that the oil shears first before it thickens. In this case, a KV100c of 10.2 is not because Supertech is shear stable, it is probably because it is now thickening after shearing.
I'd take this oil out another 2,000 miles without concern.
At this point in an extended oci, another 2000 miles is the kind of interval where an oil can rapidly degrade. I wouldn't say it's definite, not even likely to cause any problems. But I'd want to avoid any chance of deposits forming and agree with the OP about changing it out.