couple of summers ago!
My best advice for you will be to throw the flour away as any kind of flour should not be stored for more than a year....
If you are not really throwing it away..well then like any other flour..use air tight container...if possible keep in the refrigerator...but I suppose that is not possible with large quantities...in the container you can put a bay leaf or two that are natural insect repellants...
If buying a new stock...do not mix with the old one please...