Two of mine have been paci kids. With both of them, we chose to go the let-them-decide route (after some trial-and-error: see below). Starting at age two, we limited its use to the house, and around three we limited it to in bed, on a lap, or in the car.
With DD1, when she turned four we agreed we wouldn't buy another one-- when the current one wore out, that would be it. It happened about three months later-- it got a little tear and didn't "work" anymore. She moved on her own to sleeping with it clutched in her hand. Her teeth are fine. She's six now.
DD2 is 3 1/2. At this point, she has decided on her own that she's a "big girl" and can sleep without it. But in her moments of stress, she'll ask me to let her have it for a few minutes. She uses it to help pull herself together when she's having trouble dealing with her emotions. The rule is she has to be in either her bed or mine, while she's using it, and when she gets down, she puts it away in my bedside drawer. Her teeth had moved a little forward, but within a month or so of her stopping sleeping with it, you could already see that they'd started to move back.
Our dentist's advice was to strive to have them done with the paci before they started to lose their milk teeth-- so by around five. He was the one who emphasized with me, though, that the quantity of time matters-- that using it for ten minutes to fall asleep or recover from a tantrum is very different from walking around with it in the mouth all darn day.
I can understand that it bothers some people. But at 19 months, I think that the various benefits of baby having a comfort object far outweigh any squeamishness that adults have about it. I might limit its use to in bed, in the car, or on a lap, rather than letting baby walk around with it. But I wouldn't go farther than that. If baby sleeps with it, you might try easing it out of baby's mouth once baby is soundly asleep.
I tried taking the paci away from DD1 at this same age, and it backfired on me horribly. We'd lost her best source of comfort, and the best way to help her through things like tantrums. And without it at night, she started sucking on her lower lip instead, and walked around for four months with a big ugly blister on her face, until I got wise and gave the paci back to her.