I haven't grown for a couple years and I just started a grow with the nutrients I had two years ago. They have been airtight in a dark closet. Hopefully they will still be good!
I've read on General hydroponics' website that as long as their nutes are kept sealed (not unopened, just resealed), in a dark and cool environment that they should keep indefinitely. Not sure of the line you're working with but as long as they're synthetic you should be just fine..
as long as they don't make an rattling noises when you shake the bottles you're golden. other wise chem reactions have been taking place, and best to trash em IME