I have 3 kids, ages 15, 2 and 4months.
My 15 year old got a pacifier (we call them do-dahs here) right away. I had absolutely NO issues with them. She got it whenever she wanted. We got rid of it sometime after her 3rd birthday. That was actually a big year for her, between her 3rd and 4th birthday. She got rid of the bottle, the do-dah, she potty trained AND got a big girl bed, all in that one year. It was a big transition year.
Anyway, I just got sick of buying them, trying to find a lost one, it was a mess. So, one day, I decided I wasn't buying any more. I sat her down, we had a talk about being a big girl (lots of big girl talks that year,) and talked about getting rid of all the do-dahs. I had her gather the few that we still had in the house and she threw them in the trash. It really wasn't a big deal for us, obviously, she was as ready as I was.
My 2 year old (just turned 2 in November) still uses one to sleep. It stays in her room, after she gets up, it gets left on her bed, right next to her stuffed Mickey that she sleeps with also. I don't let them downstairs at all, because otherwise we spend an hour or so at night scrambling to find it. But, because it's upstairs, it's easy to only use it to sleep with.
My 4 month old gets a do-dah occasionally. She doesn't have a super high sucking need, but like dd2, once she's done eating, if there's still milk coming out of the boob, she doesn't want it. Pop in a do-dah and she gets her last bit of sucking need out, then pops it out after like 2 minutes or so. She also uses it to fall asleep, but doesn't need it to stay asleep. She doesn't need it much other than those two times.