  The systematic of the spontaneous fission half-lives for the nuclei
$^{242-262}$Fm and $^{250-260}$No is analyzed, within a least action scheme,
with the parametrization D1M of the Gogny energy density functional. The
properties of the dynamic (least action) fission paths are analyzed and
compared to those of the static (minimal energy) ones. The constrained
Hartree-Fock-Bogoliubov approximation is used to compute deformed mean-field
configurations, zero-point quantum corrections and collective inertias. It is
shown that a cumbersome full variational search of the least action fission
path, within the space of HFB states, might not be required if the relevant
degrees of freedom are taken into account in the minimization of the
Wentzel-Kramers-Brillouin action. The action is minimized in terms of pairing
fluctuations that explore the pairing content of the HFB states along the
fission paths of the considered nuclei. It is found that, for a given shape,
the minimum of the action in fermium and nobelium nuclei corresponds to a value
of the pairing fluctuations larger than the one associated with the minimal
energy solution for the same shape. The reduction of the action, via larger
pairing correlations, has a significant impact on the predicted spontaneous
fission half-lives improving their comparison with the experiment by several
orders of magnitude.
