It was found that the upper temperature limit of stability of hydrochemical deposited supersaturated solid solutions СdxPb1-xS (0 < x ≤ 0.18) is 405-410 K. At higher temperatures, heating decomposes these compounds in two phases: a solid solution with the equilibrium at a given temperature sulfide content cadmium and X-ray amorphous CdS. The greatest changes in the photovoltaic properties of the films of supersaturated solid solutions CdxPb1-xS during the first two years of storage at room conditions were observed in the first 2-3 months. Dark resistance varied by 20-40% during this period, the maximum change in voltage sensitivity was 20-25% of the original value.