Changing the Go To Sleep After time period on your Kobo Arc
Your Kobo Arc automatically goes to sleep if you aren’t using it for a while to save battery life. The shorter the time Kobo Arc stays awake while you aren’t using it, the longer your battery will last. You can change the time Kobo Arc waits before going to sleep to a period lasting anywhere from 15 seconds to 30 minutes.
To change the time Kobo Arc waits before going to sleep:

Settings icon.