  Evaluated $2\beta^{-}(2\nu)$ half-lives and their systematics were reexamined
in the framework of a phenomenological approach. Decay rate dependence on
nuclear deformation, decay energy, shape coexistence, and forbidden transitions
was observed. The following analysis showed distinct impacts of decay energy on
half-lives and deformation parameters on effective nuclear matrix elements.
These findings were used to predict $T_{1/2}$ for 36 isotopes of interest.
Present work results were compared with published data.
