Or you can use various glues on the handle before you hang it. Some guys like this, some don't. I have only "glued" a couple heads, and when I say this I mean glue all over the handle and then also in the space for the wood wedge. Not to the point where you get the Permabond look like on some of the new Plumbs, but just enough for a little extra sticky sticky.
I would agree with the fact of hanging it, using it, then looking at it. I am not a big fan of the metal wedge scene myself, but if you have to use one, I would hang the head, use it like you did, then put in the metal wedge. If you are going to be using the axe on a somewhat regular basis I would use only the wood wedge and then soak the whole head in order to make sure everything is tight.
Bottom line if you hang it right, you shouldn't ever have the "fly off the handle" issue. Hopefully anyway.