your controller should turn off automatically when not in use and since it's not turning off it might be broken or simply receiving some unintended stray input. triggers and analog sticks can be a culprit for stray input... sometimes my controllers get left resting somewhere and a trigger or analog stick will be out of whack so the controller never turns off. also, even if a controller looks good it may have an issue with stray input. google "Controller Test Disk" and find the xbox utility available to test your controller... it will show you on screen if any input is being registered by the controller when not in use. i've had controllers with mystery issues and this utility has always helped troubleshoot them.