The game is almost finished. The 18 stands for how many times they've made a major update to the game, and each major update had at least a few alpha and betas, so if you have been a Patreon since the beginning you've pretty much gotten at minimum of 72 builds of the game. They have announced that the only content left that's coming is Frank's story, Vickie's ending, and the female playthrough.If you have been paying 5$ monthly from the beginning of the development of this game you would have paid 240$ as of today. It has still not reached v0.2 at this rate you'll have paid 1.000$ when it reaches v1.0.
I'm guessing it will take a brake during the 3rd world war.