You can definitely become a prop. (I'm at the point where I'm trying to figure out how to 'un-become' one). I know how it happened to me: I didn't let him fuss long enough as he was falling asleep. DS is spirited/touchy so he whines, fusses and complains when going to sleep. I didn't know how long to let this go on for before coming in and shhh'ing him. Now, when he's not overtired, he expects me to come in one last time before he rolls on his side and falls asleep. :? (it's kind of cute, really, but I'd rather he fell asleep on his own. :wink:) When he's overtired, he expects to hold my arm while falling asleep. :?
You know you've become a prop if, like a pacifier/dummy, he wakes up and expects you to be there in order to fall asleep.
I just re-read the Sleep Interview. I highly recommend looking that over; Tracy talks about when to leave the room so that you don't become prop.