Per BeerSmith (Hop Age function):
Citra hops (25% HSI), 12% AA
Stored vacuum packed in freezer for 1 year would end up at 11.41% AA (or a 5% reduction of alph acids).
Stored in plastic bag in freezer for 1 year would end up at 10.85% AA (or a 10% reduction of alpha acids)
Vacuum packaging is better (half the loss of the plastic bag), but it is the cold temperature that is the key. There is no real problem storing them if you don't have a vacuum sealer.
I usually break my orders down to 6 ozs packages that I vacuum pack. The opened pack gets sealed using the re-usable zip-lock vacuum bags (with the little hand pump) .... it's way easier than pulling out the big vacuum sealer.
HSI = Hop stability Index, or the amount of AAs the hops would loose if left in the open at 70 F for 6 months.