MouseEvent listeners question

programming flash
1

I just had a quick question that some of you might know the answer to.

What is the best method of adding eventlisteners? I always see people clump them like this, so that there are multiple listeners at all times like this:

btn.addEventListener(MouseEvent.MOUSE_OVER, overFunction);
btn.addEventListener(MouseEvent.MOUSE_OUT, outFunction);
btn.addEventListener(MouseEvent.MOUSE_DOWN, downFunction);

function overFunction(e:MouseEvent):void{

}

function outFunction(e:MouseEvent):void{

 }

Ive been doing them rather like this, which makes more sense to me. Only thing is that Ive never seen anyone elses code do this and Im assuming there is a reason that Im not aware about.

btn.addEventListener(MouseEvent.MOUSE_OVER, overFunction);

function overFunction(e:MouseEvent):void{
     btn.removeEventListener(MouseEvent.MOUSE_OVER, overFunction);
     btn.addEventListener(MouseEvent.MOUSE_OUT, outFunction);
     btn.addEventListener(MouseEvent.MOUSE_DOWN, downFunction);
}

function outFunction(e:MouseEvent):void{
     btn.removeEventListener(MouseEvent.MOUSE_OUT, outFunction);
     btn.removeEventListener(MouseEvent.MOUSE_DOWN, downFunction);
     btn.addEventListener(MouseEvent.MOUSE_OVER, overFunction);
}

Thanks