Actionscript 3 :: Use A Stage Instance Rather Than Calling 'stage'?

I would like to know if there is a reason that, within an AS3 class, I would want to do something like this:

var myStageInstance:Stage;
//within an arbitrary class
var myStageInstance:Stage = stage;
myStageInstance.addEventListener(MouseEvent, someFunction);

as opposed to something that I would normally do:

//within an arbitrary class
stage.addEventListener(MouseEvent, someFunction);

There is no particular problem that I am looking to solve right now. I would just like to know if there is a reason to use one method over the other.