Feedback on mid-term: Delay between cause and effect

I was marking the script of one sister. She normally sleeps late and then experimented with sleeping early. Not seeing any difference, she decided to go back to sleeping late again. The question is whether one expects a change in behaviour to have an immediate effect or a delayed effect. Very often, there is a delayed effect. We have to patiently continue with the right behaviour until we see in improvement in our performance.