Since most of the dev time goes into writing and fleshing out characters, they could release rough concepts with placeholder text and simple directions, like how they skipped heavenly gangbang, but with scenes finished and text skipped. Then flesh them out bit by bit over time. I guess the issue there is that the scenes are tailored to the story, so they either have to retcon the story to let the scene make sense or alter the scene. Perhaps I'm wrong and it's the art and animation that takes so long, which.. get someone else.