Wayne - It might be prudent to do FCIs in stepped stages; let the filter disections and UOAs tell you when to "step up" to another interval.
Example ...
Right now, the insoluble loading is high; the evidence is apparent visually on the media and the UOA shows high wear. So run a 5k mile FCI and then cut that one apart. If the carbon deposit is still heavy, do another 5k mile FCI and repeat. As the insolubles taper off, and wear drops off, you can probably up the FCI to 10k miles, then cut and check. Then as the progress improves, up to 15k miles or 20k miles for the FCI.
I'll relate a very old experience I had many years ago, when I was a noob here. Gary Allan approached me to run some experiments with the (often hated) ARX product. I did have an issue with compression in my old Taurus engine; the rings were coked badly due to a previous owner overheating event. The ARX is a tri-ester product that works well, but it takes time. Frank told me to make sure I changed oil filters every 3k miles several times, because the junk that the esters were going to release was going to end up in the sump. And he was right; the filters did have a high level of loading.
Perhaps the lesson here is that if you're going to use an ester-based high quality cleaning agent (either as a separate additive or part of the oil product itself), and you're doing so on an older engine with high miles, then short lube filter intervals are a must. Whereas using an ester-based product on a new engine will keep the engine clean, and the filter interval can be "normal" because there won't be any junk lurking and waiting to be released into the lube stream. Can I prove this? No. But there's two reliable anecdotal stories here (Wayne's and mine) which would indicate this is a good practice to adhere to.
