i just downloaded the new version and looked at your examples,
maybe im thinking this in the wrong way, but how i tought it could be
is like when you hover a button, i plays it pingpong animation whatever happens and then stops, you probably dont want when leaving a button it abruptly stops animating
but i will recheck the posibilities, i guess you could use two tweens,
i will post examples in future
edit: i think the most dynamic way would be to have a playback mode
"pingpong stop"
so when you hover you have an in and out animation with one tween
its more a feature as you can make it with two tweens... but saves events