Board Thread:Questions and Answers/@comment-3074300-20170126190128/@comment-26727037-20181012190749

This just happened in the anime and seeing the 20 years confused me, knowing about the Curse.

Option 7: The Attack Titan is unaffected by the Curse of Ymir. It would go with the theme of them breaking free/advancing. It wouldn't necessarily explain why previous Attack Titan possessors might have died at 13 years, but as far as I know we don't have any concrete examples for it happening to Attack Titan holders, let alone many others. Eren Kruger may have just thought that it would affect him, either because it's a rumor or because it actually does affect the other Shifter Titans, so he gave it up so that he would know it went to someone who could do something, rather than a baby (if he died).

I would also tend to agree that using the power more would make you age faster, but I don't know if that applies to the Founding Titan, which seems to not use it that much but that consistently seems to get very aged after the 13 years. Or maybe they really do use memory changing a lot more than we realize.