The idle screen on your watch may be convenient, but it can also be annoying.
You may have noticed the screen on your Android Wear watch never truly turns off. Sure the brightness is turned way down and the bright, colorful display is hidden when the watch goes into idle mode, but the screen is still on. Not only is it sipping on battery power, but it's also an annoyance when you're trying to sleep or wearing it in a dark room (perhaps in a movie theater).
Google did include an option to disable the idle screen. Here are two different methods to achieve the same results:
Alternatively, you can disable the idle screen on your watch.
Either method will prevent the screen from lighting up unless you raise your arm or tap on the device. Granted, the idle screen likely isn't a huge drain on battery life, but every bit counts. Not to mention, trying to sleep with a screen lit up on your wrist or nightstand while charging is never fun.