LH switches them off but has the same recommendation to leave them on all time (which I do).
That's pretty standard on all carriers (except U.S.), but that's not quite the issue here.
Personally, I feel that the American carriers' policy is potentially more of a danger to pax. I rather have the advisary "to keep them on at all times when seated" but only have the signs illuminated when the threat is real. What the American system does by keeping them permanantly on is encourage pax to eventually ignore the signs.