The intensity of second harmonic (SH) light, generated by passing a laser beam through corona poled films of poly(ethylene oxide)/atactic-poly(methyl methacrylate), PEO/a-PMMA blends molecularly doped by 4-anilino-4'-nitroazobenzene (DO3), is studied as a function of time, temperature, and composition. SH intensity decay kinetics at room temperature is entirely controlled by the time-dependent surface potential decrease (SPD). In turn, the SPD is determined by the conductivity of polymeric films and the free volume. The latter is a function of temperature history and blend composition.