I’m not aware of rebound issues but it is my understanding that your body generates creatine from red meat but if you dose creatine, for the time that you are on it, your body stops producing it, so you don’t get incremental, you need to dose for that. And if you stop taking it my understanding is your body starts producing creatine again. My strong suspicion is it’s the same with melatonin the only question is if there is a lagged effect with either and how long. My belief is the lagged effect for creatine is small enough to not be measured in studies so yeah seems like no bad effects. I haven’t looked into the lagged effect of melatonin yet if any.