Looping a Timeline
In order for a timeline to replay, it needs to loop. This uses the behavior: go to Frame.
Making a Loop
1. Put something in a timeline.
2. Select the Loop check box in the Timeline Panel.
3. To adjust the loop double click on the behavior that goes in the last frame of your animation in the behaviors layers when you selected the loop check box.
4. You should see a behavior. Double click it to get a dialog box.
5. You can control the number of times that it loops or put nothing in the
box and it will loop forever.