I had a batch that was 3.5 years old and like new. I discarded it last year only because I moved - but I promptly rebought another 50 lbs batch.

I store it in plastic paint containers that sell for $4 at Home Depot - I've got 2 big ones and a smaller one. The small one is what I use every month, and refill from the 2 big ones.

Best sports nutrition move I ever made. I now know why sports drink companies do it - selling essentially bulk malto for a 30x markup is profitable! (If it weren't for the darn sponsorships and advertising it would be a lot better for them...)