From Social Patterns
Temporal Awards are designed to recognize specific people in a community for a limited period, for instance, Employee of the Month. Within this reward framework, the benefits associated with an award lapse after a certain period and there is no explicit requirement to revoke the reward at the end of every period.
Temporal Awards are especially valuable in eliminating the need to remove the reward from people who were formerly recognized but are now considered unworthy. Although temporal awards may diminish the willingness to make long-term investments, this drawback can be reduced if people can earn the reward for consecutive periods and enables them to sustain interest with evolving benefits.