In my architecture photography i never changed skies, but always have to do some or more cleanup.
So i look at it and decide what is quicker?; a real cleanup or a photoshop cleanup.
On one occasion i ended up cleaning the floor of a theatre...
in an other occasion an earial view of a square was very nice, but there were many stains because of a weekly market... took hours...
and then we have the windows...
and often the building is not ready yet, so i have to make it ready... or the photo is useless.