It goes off after about 10 minutes. Even if it didn't it wouldn't harm anything as long your not powering anything. The LED indicator won't even touch the battery. LEDs use such little power that sometimes they stay lit briefly after unplugging due to the residual power in the line.
Sedan Revolution #249 - 2012 SE Sport - ╠╬╝ - Ingot Silver - 201A - K&N w/ snorkel delete