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".
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".