What do Butler and Artemis agree to never do again now that this whole incident is over?

Butler is upset with the way the Artemis handles much of the incident from the time that they met the first fairy who gave them the book. In the end, Butler is even angrier with Artemis because he had taken so many risks. But what bothers Butler the most is the way that Holly was treated. Holly wound up saving the lives of Butler and Juliet against the troll. More than that, Holly had been almost human--a kind and caring human. Butler did not want ever to do any harm to a fairy again. There were times that Artemis felt something for Holly as well. When he first met her, he was taken aback because she was a female. In the end, he agrees with Butler that they should never again get involved with tasteless ventures.