How can I turn off the LEDs on the RE220 so they don't disturb me at night?

Log in to http://tplinkrepeater.net and go to Settings > Advanced Settings > LED Control, then disable LED Status to turn off all LEDs. Alternatively, you can select Night Mode and specify a time period during which the LEDs will be turned off automatically. Note that the effective LED off time is based on the extender's system time, which can be set under Settings > System Tools > Time Settings. (Page 42)