Thank you. On reconsideration, I suppose they mean "length" in the sense of "all day long." You could probably use "length" in English to refer to "duration," and be understood, but I think it would sound odd.
I think this is a good translation except that we native speakers would usually have something else to say in it's place. "dater' is maybe in the first 10000 German words, but maybe the third ten thousand in English.