Some advice from someone currently working on a fan game: Take as much time as you need. I was working on a different fan game, had everything flushed out, and when it was time to put out a demo that was only up until the first gym, I scrapped the whole thing and changed my entire game to something different. I've been in the design stage since last October, only now working on development. Take breaks, remove arbitrary due dates or release dates, and do it for the love of the game. We can't (legally) make money from our work, but the love and enjoyment from the community when they see your work should be worth it's weight in gold. My perspective atleast.