I discovered the same. Before I knew of the Energiser headlight, I bought a headlight with several settings made up by progressively turning on more white LEDS. I dived in, ripped out three white LEDS and replaced them with red LEDS so the first setting was red LED. I had to change the series resisters as well. (I always do things the hard way
). Well, the batteries ran down for the first time and the first I knew that they had was the white LEDs fading away while the red LEDS shone as brightly as always!