I've never read a book or attended a class on screenwriting....

I've never read a book or attended a class on screenwriting. I'm not opposed to the idea, but I like what I've got going on naturally and want to protect that. The one question I will ask myself as I'm re-reading a script for the 60th time is, 'Am I entertained? Still?' If the answer is 'yes,' I'll assume other people will be, too.