We took DD1's away when she hit 18 months. She only had it for naps and bedtime and during the day we'd keep it on a high shelf in her room so she couldn't grab it from her bed. Eventually she'd just start going back to her room and screaming and crying during the day for it. Then it started happening multiple times a day where she was throwing these tantrums over not having it whenever she wanted. It was then we decided to take it away.
I explained it to her best I could that pacis were for babies and she was a big girl now and she kind of seemed to understand. Then we never gave them back. It took about a month before she stopped having sleep disruptions. It only took 3 days before she stopped asking for it altogether, but for a solid month she either took an hour to fall asleep at night and/or woke up an hour early in the morning.
Her younger sister was born 3 months later and uses a paci and now she points at it and says, "Paci. Baby."
That is the saddest, cruellest thing I can think of. You let your 18 month old scream and cry for a dummy which you had placed out of her reach but within her viewpoint? And then went on to allow her to struggle to settle down to sleep for a month? Sleeping later and waking earlier, she must have been so tired and miserable.
So you have achieved your desired outcome, your LO now sees dummies as something for babies. Congratulations on that.
Heartless.