Lots of windows here!
Our housekeepers take care of the insides, but we really need a person or two to wash the outsides. It is not difficult, we have the sponge/squeegee. Take your time. A couple of hours a week will get many done; and by the time you get all the way around (500+ windows), you might consider starting all over.
Do something good for our residents, let them see the outside through a clean window!
Life is like a sewer. What you get out of it depends on what you put into it.