My experience is that antime the flesh is exposed, even if fillets are vacuum packed immediately, freezer longevity is limited.

Last year on my Canada trip I headed and gutted my salmon, then froze whole. After returning, I removed the fish from the freezer, dipped them in ice water, and then refroze, compelting this several times until the entire fish was encased in a solid coating of ice. Commercially flash-frozen fish goes through a similar process.. If defrosted slowly in a water bath, these fish, even after 6-8 months of freezer time, are almost next-day fresh, with no discoloration, flesh softness, or that "old" odor that usually accompanies long-frozen salmon.

Downside is that you end up with a lot of fish each defrost. I usually eat a couple meals, then smoke up the rest.