It depends on the content (actually, about 90% of how or when a drama will air is all about content, to make sure it’s not anything “against” the beliefs & principles of the Chinese government), episode count, time of year (there is lots of special occasions on the Chinese calendar), as well as the popularity of the main leads in the current time of Chinese dramaland because the more popular the actors/actresses are for a drama waiting to air the higher the chances are that the drama will air as soon as it finishes post-production because popularity of the mains typically equals popularity & ratings ($$$$$) for the drama

@bebeswtz, except Xu Kai had two dramas ready after Yanxi Palace and they still hadn’t see the light of the day. But I agree with you point, and I hope it’s true in that case, it seems like Yang Zi dramas don’t have to wait long for air date.

Xu Kai got people’s attention after “Story of Yan Xi Palace” but it was Wu Jin Yan who’s name really blew up and became popular (with a revival for veteran actress Qin Lan, the one who portrays the Empress) and she picked up a lot more variety show appearances, commercials, magazine spreads, and was even invited to lots of major fashion shows during fashion week in multiple places.
For Xu Kai, I’d say his name and popularity didn’t explode until after “The Legends” (which I know is the drama he filmed right before filming “…Arsenal” )