My mother took care of a lot of babies as I was growing up, so I just grew up thinking the time to gradually reduce pacifier use was by three/four months (tops). It's fairly easy to stop use of it at that age. It's more difficult later (but, of course, one way or another, kids stop using it eventually).
So, that's how I did things with my own babies too.
It just seemed to me that newborns (and slightly older) do have that sucking instinct, and the pacifier serves a purpose for them. They're more easily frazzled than older babies too, so something that calms them (without over-feeding them) is good.
By three months they're well past that newborn/sucking instinct stage (at least in the same way they have it when they're newborns). Calm, secure, babies who aren't hungry just don't really need that particular kind of comforting by the time they're three/four months old. It's mostly the first two months when they're so new and kind of getting "up and running" with being in the world; and with their digestive, nervous, and other systems (as well as growing past newborn instincts/reflexes).
BUT, if someone wants to give a pacifier to their baby for two years - their business, of course. :)