User blog comment:Xilinoc/Ch. 564 (Mask is too fabulous to live)/@comment-26420452-20140116063819/@comment-26420452-20140116143811

I think that he kept Mask around for so long so that we would be eager to see his death. He made him extraordinarily strong in order to show how much Renji has grown strong (Now imagine how strong Byakuya and Ichigo have become...).