Don't quote me, but I seem to recall a sustained 160F measured in the sump is good for cooking off moisture. Obviously the hotter the better, so maybe that isn't such a good answer, but it's the one in my head. Oil is pretty happy at around 220F, but ideally not much higher.
Plus there is the issue of where, exactly, you are measuring the oil temperature. There will be a wide variation, even in the same motor, depending on where you are picking up the temp.
That's why they say to watch your oil temperature when it goes higher than the typical number for your vehicle, rather than giving a specific temperature to watch for.
If I were concerned about it (I'm not) and wanted more info, I'd be looking at the higher reputation oil cooler manufacturers for guidance, so that's where I would be pointing my Google search terms.
Moroso
Derale
Setrab
Canton
... and some of the Hot Rod people.