A little more info on sword skill uses

"Sword Arts are ranked on a scale from E to S. E rank techniques can often be used as many times as a character wants, though they rarely have insane effects. On the opposite end of the spectrum, S rank Sword Arts usually have ridiculous effects with long charge times and few uses."

Could we get some more info on this? I am not exactly sure how to pace my sword skills as people are going to have different opinions on how many times is too much.