That applies only when you perceive the danger to your life to be at that present moment - not when you fear that someone may come back a day, a week, a month later to hurt you.
Again, if that was the standard, then you could kill anyone you wanted to - even if they were completely unarmed - and claim that you honestly believed that they were going to bring a deadly weapon to kill you the next day.
Well, yeah, which is one of the reasons you really, really, really gotta’ behave yourself in some states.