I was thinking Aging would be passive.
I also was thinking it would work something like this.
first 2-3 turns stats are improved.
then creature develops current or new skill for 3-4 turns.
finally stats begin to fade till the creature dies.
If a creature with Aging is rewound
, it loses 1 turn of Aging and continues to get younger until it is sent back to deck.
, unless it is rewound again.
I know this is complex, but it is just what I was thinking.