Goodbye Pacifier?

We've tried (unsuccessfully) to get Rai to part with his pacifier for several months. With the pacifier, he can fall asleep in minutes. Without it, it can take him hours. I guess he's not quite ready yet although we don't want him to be five years old and still carrying it around. Kotaru on the other hand, needs only some trees and the fresh air to pacify him. A quick walk outdoors is good enough to put him to sleep.