For DEEBOT with random pattern (Deebot 500, DN79 Series, DM81/80 Pro/81 pro, DN78, DM85, SLIM2, MINI2), it will continue to clean until its battery runs low. Then it will automatically slow down, and begin returning to the charging dock. It might take a while, and sometimes head in the wrong direction (like a drunken sailor), but it will eventually get there.
For DEEBOT with programmed pattern (DEEBOT OZMO 930/937, DEEBOT OZMO 600/601/601, DEEBOT 900/901/907, DEEBOT600/601, DEEBOT 710/711, DM88), it will return to charging dock if its battery runs low or it completes its cleaning cycle.
The DEEBOT OZMO930/937 and DEEBOT900/901/907 comes with LDS (laser distance sensor) and they can remember the location of the charging dock, so they can find the charging dock more easier.
If you wish to send your DEEBOT back to the charging dock 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 charge/home button. You will notice the DEEBOT will stop vacuuming and will head back to the charging dock.
While your Deebot may take several minutes to find its charging station, it will eventually find it. 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 probably 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.