Didn't she say that it was just an exercize she used to focus, and wasn't really ALL that necessary?

I don't remember where I read that. I'll have to look it up....

The problem with Zatanna is that her power-level is not clearly defnined. She certainly has some sort of limits, but what they are is not clear.

In one of her original appearances, she was physically weakened when she over-exerted herself. This happened when she was fighting a warlock alongside Green Lantern.

In the 80's, they tried to limit her powers to elemental magic, but that didn't last.

You're also all apparently forgetting that Zatanna indicated both in JLA and Adventures of Superman that's she just about used up all of the magic reserves that she had, and that she isn't getting any more because of the events of Day of Vengeance. She might've stopped Despero and re-erased a few memories, but she didn't have enough juice left at the end to teleport herself back to the dressing room where Superman found her ...

You're so smart JacinB

Which ties into her current mini where one last spell pretty much pushes her over the edge (and has bad, BAD consequences), resulting in her losing her powers.

Yeah, I know. It's a blessing and a curse.