Your best option would be to call or email Tetra Fauna here:
http://www.tetra-fish.com/contactus.aspx
I'm guessing the phone call would be the best choice.
I mean, it's not like the turtle food has anything but dried components to it, but meanwhile, it's still a food and can get moldy or fungus or whatnot. I'd say your best option would be to see if you and a few people can go in together on the cost and split the food up. The next best option would be vacuum sealing the bulk of it and keeping it in a cool, dark place.
I mean, I bought the 3.7 ounce bottle about 15 months ago and I'm around 2/3rds of the way through it. By those calculations, it would take me over 22 YEARS to go through that big bottle. I'd have thrown out the left over long before then for fear that it went bad, I mean, 22 years is a bit long to trust that the food is still fresh.