User blog comment:Soulreaper1234/What's up with Ichigo and his BANKAI, is it in constant release?/@comment-1510183-20100916030612

Unlike other Bankai users, Ichigo can keep it for long periods of time. ::

Byakuya Kuchiki noted that Ichigo's Bankai was a COMPRESSION Of his Reiatsu, while everyone else's were Vast Expansions. This was their Final Fight on the Soukyouku Hill.