We started throwing a ball for Willow out on walks as you see other dogs doing all the time. At first she was really good and even dropped the ball at our feet when she wanted to us to throw it. After a while she realised she was being put back on the lead now she runs out reach when she has a ball. She has really good recall and doesn't stray too far when off the lead. I only give her the ball if she is on the lead throwing it so she can catch it even then she is reluctant to drop it or give it back and treats don't work as the ball is higher value.