Eh…it’s a comfort for them. It’s like a blanky. My son is 22 months and still uses a paci at naps and bedtime, although really only uses it to fall asleep - once he’s asleep, it’s out of his mouth and he’s usually good without it for the rest of the night. At daycare, he’ll sometimes sleep without it. I’m sure if we tried, he’d give it up, but right now, it’s not high on my list of priorities.
It also helps him when his teeth are hurting. He has four teeth coming in at once right now, and I’m not going to take away something that helps with that pain.
We started it our second night in the hospital, at the suggestion of a nurse. I was breastfeeding, and it didn’t affect his ability to breastfeed at all. In fact, it saved our sanity because he actually started sleeping longer stretches in between nursings. And I got some sleep, which was a huge help, too.
Generally speaking, the best thing is to offer the breast for all sucking needs. Babies need to suck not just for food, but for comfort, and it’s perfectly valid to offer the breast for comfort. So comfort nursing is not a problem for baby. However, the way our culture is set up, it often is a problem for mom, since we have to tend to older children, do housework, work outside the house, and so on. And some kids (like my new one) have such huge sucking needs, their mothers would never get anything else done.
I’d say if you’ve been nursing for a few weeks with no problems, or if you’re formula feeding, there’s no harm in using the binky. Whatever helps you survive! If you’re nursing, just make sure you’re not offering the binky too often - what I’ve been doing is offering the breast first, and if she’s not hungry, I give the binky. That way you make sure baby is nourished and your supply is intact. (Though binky use is associated with earlier return of your period, bummer.)
Of course, Claire is a rare baby - she gets MAD when she wants to comfort suck and gets milk as well. So she’s a pacifier girl all the way. We tried the binky with Chloe too, on the advice of our lactation consultant. Chloe would finish eating and then let her latch slide, staying just on the tip, which gave me sore nipples. Eventually she found her thumb, and it was great. Now the dentist tells me the thumbsucking put pressure on the roof of her mouth, making her palate higher and narrower, so there’s some concern all her adult teeth might not fit. So I think that’s a big advantage of the binky - it doesn’t push up like the thumb. Plus, as others said, it’s easier to take away, and harder for the kid to use accidentally when they’re trying to quit.
Bottom line: as long as the baby continues to be fed well, do whatever you need to to preserve your sanity!