Just a couple of comments...
I think you would have to work really hard to get an engine to this bad a state. Maybe never ever changing the oil and then just refilling the sump when the red light comes on (something I confess I've done but only the once!).
Most US PCMOs are pretty good in terms of their oxidative stability on account of the fact that they're made from Group II base oil (at least) and you have tests in GF-5 which if anything, 'over-treat' the oil with antioxidant, dispersant and detergent. Under normal use, I'd guess most oils would be dark and see some TBN depletion at 5k miles, approach total TBN depletion by 10k, followed by total collapse of the oil accompanied by serious sludge deposition at somewhere approaching 15k.
Sludge always forms very rapidly as a result of condensation/polymerisation reactions forming big molecules which are inherently insoluble. The process is usually 'visible' as a rapid rise in the oil's viscosity. If you haven't see a rise in KV, then you almost certainly won't have sludge.
On last thing. The tests used to demonstrate the 'cleaning power' of oil are IMO a bit artificial. You run an engine to produce some sludge but deliberately stop the test before it gets too bad. You then drain the oil, whack in the good stuff and immediately restart the engine and see what happens. Because the sludge is relatively fresh and present as a relatively thin layer, it can in time be reduced/removed. However had the sludge had time to thicken up and 'bake' (like in the photo) then even the best oil would struggle to make a dent in it.