Creating an EventClient in the usual way implies creating two threads, a lease-renewal thread and a notification-fetching thread. If the EventClient object is subsequently discarded without having called its close method, it will never be garbage-collected and its two threads will continue to exist forever. This is because the threads have a strong reference to the EventClient. It would be better if they only referenced it weakly, and if they exited as soon as that weak reference was cleared.