Matthew 12:43-45 gives me the impression that demons are constantly in the lookout for humans with "open doors" to inhabit. They find no comfort in living anywhere other than a human.
43 “Now when the unclean spirit comes out of a person, it passes through waterless places seeking rest, and does not find it. 44 Then it says, ‘I will return to my house from which I came’; and when it comes, it finds it unoccupied, swept, and put in order. 45 Then it goes and brings along with it seven other spirits more wicked than itself, and they come in and live there; and the last condition of that person becomes worse than the first. That is the way it will also be with this evil generation.” (Matthew 12:43-45 NASB)
In contrast, Ephesians 6:12 appears to suggest that the demonic forces spend most of their time in the heavenly places:
12 For our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places. (Ephesians 6:12 NASB)
Where do demons spend most of their time: in humans or in the heavenly places? Does the answer depend on the rank? What about high-rank demons, principalities or Satan himself?