When your Deebot is out cleaning, it will continue to clean until its battery runs low. Then it will automatically slow down, and begin returning to the charger. It might take a while, and sometimes head in the wrong direction (like a drunken sailor), but it will eventually get there.
If you wish to send your Deebot back to the charging station early, you can use your remote or the app to do it. First, press the Play/Pause button on the remote, then you can press the home button. You will notice the Deebot will stop vacuuming and will head back to the charging station.
While your Deebot may take several minutes to find its charging station, it may occasionally run out of power while looking. It helps to keep your charging station in a clutter free area, with at least 2 feet of clear space on either side of the station.
While you don't want the charging station right in the middle of the living room, it does help to test various locations for the charger. The charging station sends out a low power radio signal that attracts the Deebot. Sometimes, just the slightest location move of the charger can really help your Deebot find its way home.