You can create a backup schedule. If you choose to do a direct "sync" then you can keep the external drive plugged in all the time and it will backup as changes are made. You can also do a scheduled update e.g. once a week or month. I suggest a cloud storage system (Carbonite, Acronis, WD MyCloud,...) of some sort and one of these on a scheduled backup that you do not always keep plugged into your computer just in case lightning hits your system or you get a virus that attacks all of you storage devices.