If I heard right, you can do it eveyday on December. Is it a good idea to do max the Aeon social link on December, or is it a better idea to do it as soon as possible? Cause if you're maxing all social links, I'm pretty sure you'd have maxed out almost all of them by the time of December.
I personally get a rank or two with her before, but the majority of her Social Link I do in December. Considering the circumstances of the month itself, it's a better idea to wait until December to do her Link.
Blades will bleed. Shields will shatter. But as the light fades, will The Hero rise again? Or will Darkness reign? ~ Zelda TP Trailer 1
Doing it all in December can be a waste time though, once you start having nights where you have nothing to do (aka no stat leveling or Devil and tower.) you should start focusing on leveling Aeon and use the fortune those free nights so you do not have to spend time to get close to a rank up she can take a lot of points.