Throw another quart in there, and run it another 5-7k. The UOA easily supports running at least a 20k mi interval.
A useful strategy to doing extended OCI's is to stagger the filter change intervals. Most people do the oil change, and the filter change at the same time. One might consider doing a filter change every 15k, and an oil change every 25k.
Glad to see another committed long-drain person here. Freedom from messy oil changes, the hassle of handling used oil, a much cleaner intake system, and longer O2 and cat life are very positive attributes!
