This is a long standing battle.. I personally crush 50 lbs. of base grain and shove it in a cooler; only 40 lbs fit so I bre that day. I have used base as old as 5 months, crystal/dark malts should keep longer; less moisture. MY THEORY ONLY.... Keep the little critters out and it should be fine.
Malt Vault
Best way to store grains?
whole
It's best to store grains whole until ready to use then mill soon before brewing. Keep them in an airtight rodent proof conatiner if possible in a cool place. Freezing sounds like a good idea for prolonged storage though I've never heard of anyone doing this. Several months of proper storage of whole grains should have little if any negative effect.
Watch out for humidity...
A couple of years ago I kept about 5 lbs. from a 50 lb. bag of malt over the summer. I also had a pound or 2 of crystal. When I started brewing again in the fall it was kinda tough milling the grains. I'm gussing moisture (humidity) in my basement/brewhouse was on the high side during hte summer and caused the grain to change. I didn't notice a difference in brewing, just in milling.
Best way to store grains?
What is the best way to store grains like Black Patent or Crystal? And also how long can they be Stored? Will freezing work?