Hi Cecilia,
I am dealing with a similar situation at this end.
A 3 month guest with no previous experience on Airbnb just left. I have hardly any hangers left, and a container I lent him to store food has gone.
How do I know? Because I drove for 3 hours yesterday taking him to another city so he could relocate. As I helped offload I noticed these things. I didn't say anything at time time - I did not want to cause a scene in front of his friend - but today I sent him an email. He insists that the hangers I dropped off are his, and he will deliver the container at some point in the near future. I have to take him at his word. And I apologized.
I do long terms. There is no algorythm to determine who will or will not work out, just your own confidence in your abilities (and eventually, your ratings history). Instead, there is a gut feel that things are or are not working out. You can look back in hindsight, but even a guest with multiple positive reviews is a risk. All you can really do is to control your own behaviour, do your best, and what you could do better next time.
Who cares about hangers and a tub? If I examine my own behaviour, part of it came from the frustration of constantly providing over and above service that was taken for granted. It's a $21 dollar a night room; I made a fair chunk of money on it; that's my reward. And it's a 3 star review waiting to happen. I can always find ways to generate 5 stars with short terms to offset his review.
And that's the real beauty of long terms. They're just one review, and a lot more cash in the bank.