Having the story completely written out, beta'd and grammar checked is one of the best ways to do a fanfic. That way if things get busy at work or elsewhere the story is ready to go. It can be posted weekly without long interruptions.
One other thing: leave the finished story with a trusted beta, just in case the unexpected happens and you cannot complete the story.
I have noticed that there are several excellent stories forever stuck in the WIP stage for whatever reason, but this way the fic is done.
Just some thoughts.
By the way Lex is my favorite villian! When I did Stranger in Our Midst he remained free.