Ultimately, yes, it is okay to leave your cooker on when you are not at home. In many ways, this is what these units were designed for in the first place. The more chocolate you use, the more stirring you will have to do, so it is sometimes not feasible to leave fudge in a cooker for hours at a time. But it is certainly more time-efficient than melting chocolate in a pan and constantly having to stir the ingredients. With this in mind, low heat settings are optimal for slow cookers as this works towards preventing a ruined batch of chocolate fudge.