When are you finished writing your screenplay?  This is one of the most common quandaries for all writers, which often has them pacing circles around the kitchen in the wee hours of the night.  The pros usually write and rewrite and revise up until, well, the last possible second before it’s contractually due.  Often times, they scribble itsy bitsy revisions well past the deadline, much to the chagrin of the exec in charge.   Note:  Best not to give the guy paying you agita with a late draft.  It’s a bit more nebulous for the aspiring writer.  Sure, you can set yourself goals, but at the end of the day, it’s pie in the sky, right?  I’ve seen many a wannabe scribe take six weeks, six months or even six years to complete a script.  (Yes, six years.  Don’t laugh.  It could happen to you.)  And like Ford Pintos, many scripts are just abandoned.  Once you’re swirling around the dark bowels of the second act trying to figure out just how to get a stripper with a heart of gold plausibly through Yale law, you might get stuck, lost, and realize it’d be easier for you to go to law school than finish your script.  I think the best rule of thumb for knowing when you’re done is when you start rewriting what you already rewrote and then change it back to what you originally had written.   You get there, put the pen down and step away from the pad.  After all, writing is subjective.   There is no correct answer.  No X = 3.14.  Just make the script the best it can be today.  Then send it out.  And start another one.