It depends on the hops. Some will fare better than others depending on their 'stability'.
If you use BeerSmith you can calculate the loss of alpha acids over time'
For example, Cascade (one of the worst for storing) will lose about 17% of it's alpha acids (bittering properties) in a year when stored in the freezer (0 F) in a 'Barrier Package/Jar'. If it were me, I would assume it's other properties were similarly affected (no evidence for this) and increase the amount used in a recipe by 25% (a 20% drop is the same as a 25% increase).
For reference: If those same hops were kept in the freezer in a vacuum sealed bag, the loss would be closer to 11%.
Hope this helps.