If your relationship has resulted in 'a break', because one party or the other needs space, and they then return, it should only happen once. The whole purpose of a break is to decide whether to continue with the relationship. When that has been decided after one break, then that should be it.

If however, you are left going through several breaks, that usually means you are choosing to hang on, hoping that it will eventually end, and you can resume the relationship. It also means that you are being used, and it also could mean that your girlfriend isn't sure she wants to fully commit to one man.

If the first break didn't result in her making up her mind if she's in, or if she's out, then it is time for you to step up, and set some expectations of her. My advice is to say to her that you will wait until the end of the month (or whatever is appropriate), for her to decide one way or the other so you can get on with your life. During that time, don't initiate contact, and there should be no intimacy.

It's the only way to stop a person from having one foot in a relationship, and one foot out.

how often do women return when they say they need space

As often as you put up with that crap!!

Why are you waiting would be my question. I mean have you nothing else to do after you get dumped?

I second what talaniman says
But also you have to wonder why she would say this in the first place,
Try talking to her about this,
There's bound to be a reason she said this.
Maybe she feels you're smothering her too much
Or maybe you're going too fast for her
Like what j.d did in an episode of scrubs,
I don't know,
All I do know is if you have problem or you don't know you do,
Ask... and if so and they can be fixed
Fix them before it's too late.