@twopointonefour: I don't generally have Kishin so I usually can practice getting 5 stacks, that said though it really depends on whether it's worth it to do or not. Like if 0 stacks or 5 stacks is going to have the same TTK (time to kill). If it doesn't change then I probably won't bother. In bosses though, I make attempts to keep up 5 stacks all the time.
It's just a lot of fun nullifying 1hit ko's or 90-99% hp attacks