Do you actually get to take a break or a rest when finishing the sprint work early? In 10+ years of doing sprints, I don't think that's ever happened to me or my team. In practice if we finish early (which is rare, maybe 1 in 5 sprints) then we try to jam in some refactor or performance fix or bug fix or something, and that ends up taking at least the remaining sprint time. There is never a chance to catch a breath.