I got function in Flash (Action Script 3) - that makes snowflakes falling. Now i want to make this snowflakes appear on screen only for 3 seconds. So I'm trying to use Timer class but i got problem:

var myTimer:Timer = new Timer(3000, 1); 
myTimer.addEventListener(TimerEvent.TIMER, snowflakes);
myTimer.start();

function snowflakes(event:TimerEvent):void {
 //snowflakes faling function
}

In this case snowflakes appear after 3 seconds and stay on the stage forver...So its kinda opposite what i wanted. I want them to appear from the very beginning then disappear after 3 second. How can I do that ?