Use of "will be"


I would like to know when we can use “[color=darkblue]will be + ing” instead of “[color=darkblue]will”? I mean, I have seen many people use “[color=darkblue]will be” when “[color=darkblue]will” is sufficient.

I will be leaving for Japan by the end of this month.
I will be calling you by 9 today.



By emphasizing the durational quality of the action, it expresses added emotion (enthusiasm, concern, etc).