The cheaper ones tend to break much more easily in my experience. The beads will jam up and the motor will get burnt out. If you clench down on it, it will burn out much more quickly. The higher end ones definitely last longer though (the Jopen Vanity line, for example). I still try to be very careful not to clench down while it rotates, even on my high end ones, because I know how hard that is on the motors. When I want to clamp my muscles down I turn off the rotation, and clench down to my heart's content.