What age did you take your childs pacifier away?

I babysit an almost 3 year old and he still has a pacifier. I take it away from him right after he gets up and I only give it to him when he goes to sleep. Should I start taking it away from him during the day when he takes his naps also and only let him have it at night. His mother lets him have it all the time when she is home. She thinks that he is going to give it up as easily as his brother as soon as he turns 3, but he is not like his brother in so many way. They are like night and day. Should I get him used to not having it now, so when he does turn 3 it doesn't shock him all at once when it is totally gone?