User blog comment:Tristateballer88/Healing Possibilites and The Princess/@comment-5398287-20150131174400

The ability to heal any wound with what seems to be a simple touch is already very powerful. It makes sense to me that there would be some limitation on that ability, as most Devil Fruits have; in this case, the healing only working on a wound within a certain window of time (maybe 24 hours) after it's inflicted would make sense.

Of course, Oda could have Kyros healed with a loophole along the lines of "his body hasn't aged because of the Hobi Hobi no Mi, so the window is still there," so who knows.