Board Thread:General Discussion/@comment-24382631-20140105033403/@comment-4957813-20140105052032

Xilinoc wrote: In Ichigo's case (at least with his Quincy powers-powered Bankai), he can maintain it for at least 3 months straight because all of its power is compressed into a small form, so take that as you will.

Even then, it will still eventually run out. It can only stay that long simply because of Ichigo's already incredible reserves of Reiatsu and the efficiency of that Bankai's Reiatsu use.