Why won't you limit break?

[Canadane]

I hate using LB on the first boss. Cause everytime someone does I never have 2 bars at the end on the last boss where it counts. So Yes I save it until the last boss.. and around 10% cause it's kills instantly at the percent. But it only works if I have TWO bars.

Why save it for the killing blow? Why not hit it as soon as you have those two bars to make the kill just a bit faster?