It's pretty common for me to incubate story ideas for quite awhile before actually writing them. I'll pound out a beginning - a couple of chapters or a few thousand words - and write up an accompanying outline of where I think the story might go, who the principal characters are, etc. Then I'll find that the idea hasn't formed enough in my head to be really confident writing it yet. Thus, it rests in a file somewhere until I'm perusing old ideas looking for the next project to finish.
I've got dozens of those, but there are always the principal ones which tend to be often on my mind. One such that I've mentioned here before is a play called ThirteenthNight. It is a sequel to Shakespeare's Twelfth Night, dealing with a revenge plot hatched by the wronged Malvolio.
I wrote the opening pair of scenes to 13th Night almost two years ago. A couple days ago I added the first new words since then. It always feels good to take up an old project - especially when new ideas come rolling in more easily than they had when you began.
I don't really intend to become a playwright. The stories I like to tell, by and large, wouldn't translate well to the medium of the stage. Still, there are certain elements to any form of creative writing that are transferable. Attempting to mimic the style and quality of Shakespeare is a formidable task (some would say I'm guilty of hubris for even trying) but I'm confident that in this case, even failing to do it well ought to be pretty damned hilarious.