In your experience, roughly how long do carbon brushes last in your polishers before needing to be replaced? Obviously it would depend on how many hours a day the machine is being used, so let's go by an average of the machine being used five days a week for maybe five hours a day.
Also, have any of you ever had problems with the springs twisting up? It's rare, but we have had that happen in a small percentage of our machines, and we're not even sure what causes it.