Best way to store it is as follows:
Boil 5 gallons of water
Add the 2 pounds of extract to the boiling water
Purchase and add an additional 4 to 6 pounds of DME
To help preserve the freshness of the LME, add 1 oz of hops (your choice) with the DME and LME
Boil water for about 45 minutes, add 1 more oz of hops (your choice, for freshenss of course) and boil for 15 more minutes.
quickly cool down and rack to a sanitized carboy or bucket. Wait 3 weeks and put in bottles or a keg.
Your LME will last a long time this way!