I believe the appropriate answer is a cooling-off period. The cooling off period us described as the state of returning to the offender's usual way of life between homicides. The key distinction between the serial killers and mass or spree killers is this emotional cooling off period in which the killer blends back into his/her normal life.
Two traits that represent a sustainable society is an emphasis on egalitarianism - where there would be a tendency to strive towards a society of equals. Another would be an emphasis on using renewable energy.
On the other hand, an unsustainable society would have an emphasis on using fossil fuels due to being cheaper and having an ever-increasing productions of goods, not considering how taxing this might be on the planet.
