Louisa took a thoughtful moment before speaking, "I guess, sir, that it depends on the charm. Like... the Glisseo charm we mentioned in the Girls' dormitory doesn't seem to wear off by the end of the semester. It wouldn't finish till someone cast "finite" on it probably. While, the levitation charm lasts only as long as you're focused and willing the subject to stay suspended in midair. So.. it depends." She had uncertainty in her tone voice.