  The magnitude of the flux superpotential $W_{flux}$ plays a crucial role in
determining the scales of IIB string compactifications after moduli
stabilisation. It has been argued that values of $W_{flux}$ much less than one
are preferred, and even required for physical and consistency reasons. This
note revisits these arguments. We establish that the coupling (g) of heavy
Kaluza-Klein modes to light states scales as ${M_{KK} / M_{Pl}}$ (hence is
suppressed by two third powers of the inverse volume of compactification) and
argue that consistency of the superspace derivative expansion requires $gF/M^2
\sim m_{3/2}/ M_{KK} << 1$, where $F$ is the auxiliary field of the light
fields and $M$ the ultraviolet cutoff. This gives only a mild constraint on the
flux superpotential, $W_{flux} << V^{1/3}$ (where V is the volume of the
compactification), which can be easily satisfied for order one values of
$W_{flux}$. This regime is also statistically favoured and makes the
Bousso-Polchinski mechanism for the vacuum energy hierarchically more
efficient.
