I know it's not totally relevant, but I'm going to take a quick detour into ser and estar, because I think they are useful concepts for becoming and being.
I don't like thinking of those two verbs as a way of distinguishing things that are permanent and things that are temporary. I like to think of them as things that are fundamental and things that are localized. (Localized probably isn't the best word, but I can't find another one at the moment.)
Ser is what you use to describe what is fundamental to something.
If someone is a doctor, if someone is American or Dutch, if someone is tall -- that's "ser". Shaquille O'Neill wouldn't be Shaq if he were short -- it's a necessary quality of his. Now take the doctor. If that doctor is bloody, we don't use "ser" to capture that because being bloody doesn't change what is fundamental here: the doctorness of the doctor.
So thinking about what is fundamental works well with Becoming because it gets at a fundamental essence. (Unfortunately Becoming implies a change into something, whereas "ser" captures a truth independent of any change. This implication is the drawback to using English here.)
Estar I'll explain another way. It comes from the Latin for "to stand", as in, "I'm standing by the door." The reason I like thinking of it, and of Being, this way is because it puts the focus on where you are. Yes, it's likely temporary -- just like standing by a door is temporary. But when someone tells you where they are standing, the focus is put onto where they are, not how long they'll be there.
So, yes Ser/Estar are good to think about, but I prefer this way of doing it.