I asked my LHBS about keeping LME over time and he thought mold might be a problem with any air introduced. I bought a 33 lb. jug to save quite a bit of money. Took 5 half-gallon plastic milk jugs, washed thoroughly, sanitized, then filled them to the brim out of the bulk jug. Placed the caps on loosely, squeezed out what little air was left in the space until syrup was squeezing out, then tightened the caps and put them in the fridge. I've got two left that are about 2 months old. Each weighs almost exactly 6 lbs. -- good for most 5 gallon batches of the styles I usually brew, plus one partially "full" one to top off recipes.