I have one in the works right now. It takes about 4 hours of work to set up a minimal plot, and it's not something easily play tested. I usually have to restart the module many times and clear campaign (persistent) variables to test different paths. Campaign variables stay with your character whether or not the server resets, so once you choose a particular course of action, it sticks.
To tell the truth, I'd rather you guys discovered the plots for yourself when I finish them, but it does take a lot of time to set them up. I'm also always interested in new plot ideas.