I think that the quickest wearing components in the control arm are the ball joints and not the control arm bushings. Generally replacing the whole control arm is in order. You can tell if your ball joints are shot by jacking up the vehicle and grabbing the tire at the 12 and 6 O'clock positions and rocking back and forth for play. Symptoms of bad joints include uneven tire wear (usually edges) and knocking when turning or loose feeling in suspension.