When used to long, the ball can come off a ball point needle. That can cause real problems with the way your machine sews. I was told by several different people that you should change your needle with each project. They said it was like pounding a well with a dull point. Your machine has to work harder and harder to drive the needle through the fabric. Eventually it will cause parts of your machine to wear out. I figure a new needle is a whole lot less expensive than a new part for my machine.