When do you start playing a new sim?

A bit of "All of the above" at times, but mostly it depends on the sim I'm playing at any given time and how invested I am in their ongoing story. My "play" is really a creative process for stories, so sometimes it's a little like work. If I get bored, it's usually because either something in the story isn't working or non-story (and non-game) factors are invading my playtime. If it's story stuff, I do something to shake it up and see what falls out. Sometimes that means making new sims to throw into the mix, and sometimes it just means solving puzzles of a sort as I search for ways to make that particular story better.