I guess its "possible" they lost some potency for bittering while frozen so long. But if they smell nice, use em.
I know alot of hops can keep for several months at room temp. I have personally kept them in a Re-sealed bag in the fridge for a year. I wouldnt hesitate to use a frozen vacuum sealed bag. (but i cut alot of corners)
I have used hops that old and had good results. The key to storage is to make sure that they are dried completely and vacuum packed. I had some that were not dried at all and they got a little icy. The beer turned out fine, though.