This group from the Univ. of Arkansas looked at the impact of freezing on the tenderness, water-holding capacity, and color of broiler breast fillets for up to 8 months.
Their conclusion: The results suggest that for optimal tenderness, frozen broiler breast fillets are best consumed within 2 months of freezing.
Because I am a big fan of frozen chicken fillets, this is valuable to know. Personally my experience has been that frozen chicken fillets beyond 2 months are still okay but the taste is not that great and the tenderness makes it almost unbearable.
Photo of a the cute chicken by Wen Rou. Used under a Creative Commons license.