This work reports the rubber electrostatic potential due to repeated strain as a function of time for periods as long as the lifetime of the sample. Rubber potential depends on two main contributions: hygroelectricity added to the mechanochemical reactions evidenced by spectroscopy and microscopy/microanalytical experiments. Hygroelectricity produces fast periodic charging in phase with rubber strain, while a slower charging process is assigned to the mechanochemical reaction products, in conjunction with residual hygroelectricity. This result explains the significant negative potential displayed by rubber over long periods in the absence of any external applied voltage. These findings may contribute to improving dielectric elastomer performance in many applications that are currently of great interest in robotics and energy harvesting. Additionally, electric potential real-time measurements show desirable features as a tool for real-time, non-contact detection of rubber structural change and fatigue.