  Decomposition of superconductors sometimes becomes crucial when studying
essential physical properties of the superconductors. For example, the cuprate
superconductor YBa2Cu3O7-d decomposes by long-time air exposure. In this study,
we investigate the aging effects on superconducting properties of BiS2-based
superconductors Bi4O4S3 and LaO0.5F0.5BiS2, both were first synthesized in
2012, using their polycrystalline samples synthesized several years ago. We
find that 12-year-old Bi4O4S3 samples exhibit bulk superconductivity with a
slight degradation of the superconducting transition temperature (Tc) of 0.2 K.
For a high-pressure-synthesized LaO0.5F0.5BiS2 sample, clear decrease in Tc is
observed, which suggests that high-pressure strain is reduced by aging.
