Is there a certain age you can no longer king a lion?

Might be a stupid question and I feel like I should know this but:I have a G2 smilus that I was going to use to mutrep my alt, but I would like to wait the 30 days so I don't have to spend 25 GBs to do it. However, he is currently over 10, and would be well over 12, if not 13 by the time that cooldown is over.

Am I still able to king a lion that old? If so, would he stay that age, or would he round back down? like when you king an adol and it jumps up to 3yrs?