How much time do I have to save for King Hassan?

I used a bit of my stockpiled Tickets and SQ to try and summon Merlin with no luck, but I did get an extra copy of Lancelot berseker, which I've been after for a while, so that's a win in my book. Maybe I'll buy some SQ for christmas and try to summon again, who knows.
Anyways, I need to replenish my stock, so about how much time do I have to save more tickets and SQ until gramps arrives?

Oh, and by the way, good luck to everyone summoning merlin!