  Theoretical estimates for the lifetimes of several isotopes of heavy elements
with Z=102-120 are presented by calculating the quantum mechanical tunneling
probability in a WKB framework and using microscopic nucleus-nucleus potential
obtained by folding the densities of interacting nuclei with the DDM3Y
effective nuclear interaction. The $\alpha$-decay half lives calculated in this
formalism using the experimental $Q$-values are in good agreement over a wide
range of experimental data. Half lives are also calculated using $Q$-values
extracted from two mass formulae. The Viola-Seaborg-Sobiczewski (VSS) estimates
of $\alpha$-decay half lives with the same $Q$-values are presented for
comparison. The half life calculations are found to be quite sensitive to the
choice of $Q$-values. Comparison with the experimental data delineates the
inadequacies of older mass predictions in the domain of heavy and superheavy
elements as compared to the newer one by Muntian-Hofmann-Patyk-Sobiczewski, and
highlights necessity of a more accurate mass formula which can predict
$Q$-values with even higher precision.
