  We report comprehensive Raman and infrared investigations of charge-order
(CO) fluctuations in the organic metal
$\beta^{\prime\prime}$-(BEDT-TTF)$_2$SF$_5$CHFSO$_3$ and superconductor
$\beta^{\prime\prime}$-(BEDT-TTF)$_2$SF$_5$CH$_2$CF$_2$SO$_3$. The
charge-sensitive vibrational bands have been analyzed through an extension of
the well-known Kubo model for the spectral signatures of an equilibrium between
two states. At room temperature, both salts exhibit charge fluctuations between
two differently charged molecular states with an exchange frequency of about
$6\times10^{11} {\rm s}^{-1}$. The exchange rate of the metallic salt remains
roughly constant down to 10 K, while in the superconductor the exchange
velocity starts to decrease below 200 K, and a "frozen" charge-ordered state
emerges, and coexists with the charge-order fluctuation state down to the
superconducting temperature. These findings are confronted with other existing
spectroscopic experiments, and a tentative phase diagram is proposed for the
$\beta^{\prime\prime}$ BEDT-TTF quarter-filled salts.
