If I understand you correctly, you want to have the text automatically fade out a few seconds after it is shown?
I would probably do something like this: (Haven't tested the code, so there are probably typos.)
<mx:Script>
import flash.utils.*;
var fadeTimer:Timer = new Timer(2000); // 2 seconds
fadeTimer.addEventListener("timer", fadeTimerTickHandler);
// Call this to show the hidden text.
function showTheText():void{
theTextField.visible = true;
fadeTimer.start();
}
// This gets called every time the timer "ticks" (2 seconds)
function fadeTimerTickHandler(eventArgs:TimerEvent){
fadeTimer.stop();
fadeTimer.reset();
theTextField.visible = false;
}
</mx:Script>
<mx:Fade id="hideEffectFade" alphaFrom="1.0" alphaTo="0.0" duration="900"/>
<mx:Text id="theTextField" text="The Text" hideEffect="{hideEffectFade}"/>
Also, you need to be sure to embed your fonts or the effect won't work on your text. See Simeon's post for more info.