The "special timer to continue delivering posted events while there are still input and timer messages in the message queue" once triggered, runs forever. Looks like it is the result of the widening conversion to int64, which is the type of the timer id parameter taken by KillTimer. The timer's original id, used at creation time, is SendPostedEventsWindowsTimerId(~1u), whereas at destruction time the member variable sendPostedEventsWindowsTimerId, an int, is used.