1) I don't see any problems with the 25k drains. They're probably relying upon an oil vendor, not the manufacturer's recommendation. The minor varnishing is of minimal concern.
2) Going to 5k intervals is a complete waste of time/money. At best I'd probably use a Full Synthetic HDEO like Mobil Delvac 222 0w30 / PetroCan Duron 0W-30, etc., with its diesel additive pack to clean that up. Instead of whatever additives he's proposing.
If you don't care much about the car after 3-5+ years and are just going to dump it and hate chaning the oil, then these long drain intervals may be for you. (maybe a sales guy on the road all the time that doesn't give a [censored] about the car he's driving) If you want your engine to run "like new", I'd never advise anyone to go 20-25k miles, regardless of how good the oil is.
You could probably make one that would keep the engine as clean as new with 20k+ mile drain intervals but the cost would be substantially higher and it's likely it wouldn't be able to meet the current API specifications.
He's so full of it. Both cars are 2006 Toyotas. One with 125k, one with 225k. He claims "Both my vehicles reach 25k before the 1 year mark".... 12 years x 25k+ = 300k+ total miles in 12 years. Maybe he's talking 25k combined between the two vehicles, and changing both sumps when the combined mileage is 25k?
And he could … but what an extremist … if he thought that look in the hole was meaningful … why not cut back by just 5k or so and keep on rolling … he surely has never looked at oxidation plots …
It's like he had a narrative to start with … and "see, told you so" …
This is the first time I've ever heard of someone changing the filter and leaving the oil. 25k is a LONG time 90% highway or not, and 12500 miles is a little longer than I would run a normal cellulose filter.