[VBprogrammer]

I dunno, maybe where you live is a lot flatter than the roads that I drive on, but the instant I see a car coming the other way (ideally before they come into direct view) is the time to turn off full beams.

Though from a game theory point of view, leaving them on for a couple of seconds is probably ideal to remind anyone who forgets to dim their own headlights.

[japhyr]

I live near mountains, rolling hills, and lots of farmland. There are many stretches where you can see a car coming from a mile away, long before anyone's high beams are noticeable. But in that darkness, my truck picks up those headlights and dims the high beams.

[VBprogrammer]

Hmm, I mostly drive in the English countryside where most often there are hills and bends, bushes and trees, houses and hedgerows. Seeing another car a mile away would probably mean both are heading into a wide valley, in which case the geometry makes it less important.

That said, I'm still not convinced your truck isn't doing the right thing. Even a mile a way you've got perhaps 30 seconds before you are passing each other. Is there much to be gained by leaving them on for a few more seconds? Seeing another car heading towards me is a much clearer and less likely to be forgotten trigger than "ok, about now my lights are probably getting annoying".