In our drama wing at school we have another lighting rig. At the start of year I unplugged the board ect. and still saw all the filaments glowing a dull orange. The dimmers had been left on but the lights do not go completely out, they just glow. Most of the lams are rated at 400 hours but these have lasted about 17,500+ hours. Saying that it might be a possible fire hazard, I'm not sure but they've been on for a couple of years.