Sleep disorders are universal and occur at any age. Some disorders arose as early as childhood or adolescence and (may) persist into adulthood. Yet both the clinical symptoms or the burden patients experience depend on the stage of development one is in. Symptoms may disappear or seemingly show themselves in a different way. This differentiation in age stage coupled with a longitudinal methodology can be a source of new information that is underutilized in sleep medicine to this day.  Information can focus on recognizing subtypes or specific phenotypes as well as on new pathophysiological insights that may allow the addition of new diagnostic criteria. Moreover, through this type of research, defining vulnerable, or protective factors in a longitudinal manner - throughout life - may be of great importance to develop more successful selective treatment protocols.