When do you start playing a new sim?

Whenever I feel like it. I have sims I've created who have never been played, and others who get played quite often and moved to different worlds to explore. I like to feel inspired when I start a new sim, and I'll decide pretty quickly if they are going to work out or if they'll just become a background sim, waiting for the right moment to step into the limelight. Or to fade into the twilight, rarely seen as anything other than a random townie.