I bought a plastic 3KG tub of Apiguard from Dadant in the fall of 2007 and used in to treat a few hives. It seemed to have worked well. But most of the gel was not used. So, I replaced the lid securely and taped it on with duct tape.
Then in the fall of 2008 I used the remaining gel to treat about 20 hives. It did not appear to work at all. I did notice that the odor of the gel in 2008 was almost nothing compared to what it was a year earlier. What is the shelf life of Apiguard. It appears that is it much less than a year.