Stupid question about cigarette lighter plug :P

[Bouchedag84]

Alright,
so for now, I just have a basic cigarette lighter usb plug that i use for charging my phone while i drive. this plug has an LED on it, which never goes out unless it's unplugged (duh).
My question is, is the cigarette lighter plug at the front of the centre console constantly powered then? If i leave my usb plug in, will it drain my battery with the small LED? Should i unplug my usb everytime?

Sorry about this dumb question. I've never owned a car that does this (and I'm on vehicle #10 lol) and wiring a damn BMW seems way more complex than it needs to be :P