The radio continuum variations from galactic planetary nebulae in the process of the central star evolution without helium flashes are considered. On the base of our distance scale we obtained empirical evolutionary dependences for the ionized mass and the hydrogen atom concentration. The parameters of a theoretical model of the interacting stellar winds (ISW) are determined to reach an agreement between empirical and theoretical dependences. In this model the time dependences are obtained for the intrinsic flux density at 15 GHz and for the critical frequency. The flux density may increase with rate of several percents until the kinematic age does not exceed 1000 years.