You would call shutdown
if you wanted the scheduler to stop scheduling the events. You don't need to explicitly do this as if you want it to run for the lifetime of your application. You would use the shutdown
method if for some reason the scheduling no longer made any sense.
An example. You're writing a CMS that offers integration with google shopping to upload product information. If the user removes their upload information (ie turned it off), you could call shutdown to stop the service doing the synchronization.