This paper introduces a technique that reduces time and energy consumed by critical flash memory operations in ultra-low-power microcontrollers. The proposed technique utilizes partial or aborted flash memory erase and program operations that proved to have no negative impacts on accuracy and longevity of information stored in the flash memory. Our experimental evaluation performed on a family of microcontrollers shows that the proposed technique can save 98% of the energy consumed for flash erase operations and up to 75% for flash program operations.