I think the thing with multi day is that you would likely lose all track of time and be fully immersed in the experience. Techniques like messing around with sleep and serving food at irregular intervals can, I’m told, really distort the captives sense of time.

Even things like putting the sub in sensory deprivation bondage and saying “see you tomorrow” then returning later in the day after a few hours with “good morning” can mess up the sense of time