LEDs should not get damaged from changing the voltage, but the LED's will get dimmer. This might actually be a good thing. If the fans are hooked up to something like a Digital Doc 5 and the fans were temperature controlled, it would be dimmest when sitting at idle doing nothing (like at night). I have a switch on my Cold Cathode, but I always leave it on though. I like my computer to make people go "hey that's cool" when they walk in the house and see it.
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