I don't think you're quite jumping the gun. :-) I started out as a kid writing in Alias Smith & Jones, then did some Man From UNCLE and Star Trek from time to time. It wasn't 'til I went online fannishly that I did any focused fanfic writing, and then it was Man From UNCLE. I joined the Harry Potter fandom later, but still wrote some UNCLE, then focused mostly on HP. After a while I eased into Starsky & Hutch while still doing HP. Now I'm equally inactive in all of them!