I like the sound of your world. I'd like to live there someday. But here's what it's like in mine:
I've been the Slayer since I was fifteen. That's when a guy with really bad taste in clothes showed up at my school and told me I'd been "called". Chosen to fight against the demons, the vampires, and the forces of darkness. My lucky day. Do you know why I got called?
Because the last Slayer died. Killed by vamps. Just like the one before her, and the one before her, and the one before her, and I could just keep on going all day. Faith wouldn't be a Slayer if I hadn't died, too. And you know how I died? Killed by a vamp. I was sixteen.