I'm moving into a house that has sat vacant for at least 6 years.  I'm quite sure it has been much longer since the windows were cleaned and it's torture for me.  As you can imagine I'm a "window kinda guy" and for me to live in a house with stained windows tears me up.  You see, after a few years of neglect even a pro can't fix a window that has serious stains embedded in the glass.  Oh well, at least the bush hides it on the outside.