Does it say anything on the package on how its stored best? Some foods you can put in the fridge, and some lose their vitamin content over time, while some do best on room temperature. I use Hikari as well, the lionhead enhancer food, but even with the biggest size they sell I never get to the point where I have to worry about how old its been.
I guess there is an advantage of having a ton of fish!
There was a thread somewhere about what foods lasts the longest in what environment, trying to find it.....
Got it --
food storage