Next double star coins weekend?

So I was wondering when the next double star coins weekend will be and if it was worth it waiting for.

So I really want to buy the new hanoverian, but I don't have enough money, so does anybody know when the next weekend will be? And if I should wait for it or just buy sc now. Thank you!

Edited to add: I feel like we haven't had one in a while, correct me if I'm wrong.