Electrically focus-tunable lenses are a type of lens whose focal distance can be varied and controlled electronically and fast. These advantages are making them suitable for many optical applications and research experiments in fields like visual optics, optical metrology, optical information processing, nonlinear optical-properties measurements, among others. For most applications, the focal distance must be known with precision and reliability, becoming an important issue that the focal distance programmed on the tunable lens corresponds to the truly obtained focal distance. However, recently, a research article has presented evidence that these tunable lenses have hysteresis. In this work, we confirmed the hysteresis of three tunable lenses, determined how predictable is the focal distance programmed under different schemes, corroborated the existence of an optical-power time drift, and proposed two schemes to be able to predict the optical-power outcome with reliability. A case of study is presented to highlight the importance of the characterization.