(See: http://forums.greensock.com/topic/7184-oncomplete-event-does-not-fired/)
"If you create a competing tween of the same object that's tweening the same property, it will overwrite the previous one by default, and if that previous one has no tweening properties left, it will also kill the tween so that its onComplete doesn't fire."
Sometimes this can be very annoying and can (potentially) break your project since there can be a lot of logic dependent on the onComplete call of a tween. Could you please add the following overwrite options:
1. Don't kill tweens that doesn't have properties, but still have an onComplete (or an other method) handler.
2. Throw an error when you create a second tween on an objects, when the first isn't finished yet.