Extending prototypes

Hi there, I am building a menu system in AE, what do people think about extending the prototype of the Window object?

Thinking of containing everything within an object. . . .

First time I have done this, any advice on gotchas? Would I interfere withat anything 'Adobe' ?

Window.prototype.myMenus = {

    myMenuBuild: function(){  alert("building menus......!") }

}

w.myMenus.myMenuBuild();