Bump!
There's a solution that's better than vacuum sealing. Do an Internet search for Brown Sugar Bear.
It's made of clay. You soak in in water, wipe it dry and put it in the brown sugar container. It keeps the brown sugar from drying and clumping. You can even put it in with a brown sugar brick and it will restore the sugar's required moisture. You'll need to re-wet it if the sugar begins to form hard "clumps".
(I always thought that the exposure to air caused humidity to "clump" the brown sugar. Not so—it's obviously the lack of moisture.)