Does Jacob grow his hair back in any of the books?

yeah.i think.but i'm remembering the question bella asks jacob in eclipse why his fur is longer than the other wolves.his response is that he cut it short 'cause jared paul and sam all did that when the joined the pack.but if im right jacob lets it grow long then cuts it again in breaking dawn.

Yes it does. In New Moon he cropped his hair very short, because it was more conveinant. But (sorry don't know exactly which book) he let his hair grow longer, because he thought Bella liked it better when it was longer. And by the camping in Eclipse it was also longer. After that it was short again