This paper proposes few ways of improving a WSN?s energy efficiency that already uses an energy efficient data routing protocol for continuous monitoring application. The proposed improvements are (i) data negotiation, (ii) development of data change expectancy, and (iii) data vanishing. In data negotiation, an active sensor sends its sensed data only when the data changes. In expectancy development, a sensor develops the expectancy of when its sensed data might change. It then adjusts its sensing frequency accordingly to avoid unnecessary sensing. In data vanishing, duplicate sensed data from multiple sensors are discarded while routed to the BS. Together, the proposed improvements can be viewed as an emulated cache where latest sensed data are always known without requiring the sensors to sense and report continuously. Our simulation results also show significant WSN lifetime increase from this emulated caching.