If they are only using it to sleep with, that's not much.
But I understand your concern.
Just keep in mind, that once you get rid of it... it may alter or temporarily cause sleep disruptions/problems. It is a "change" and transition for any child. And each child transitions and adjusts differently.
That being said... my son had his binkie for awhile... until about 2-2.5 years old. BUT, my son used it ALL day. Not just at sleep/nap. He was VERY VERY attached to it.
I have nothing against Binkies... but we, sorta had to get rid of it for my son... because it was affecting his mouth "bite."
We did it gradually, and over time. NOT rushing it. We talked about it WITH him, but with no pressure, and without nagging or sounding like a broken record, NOR using bribery or punishments or scolding. First only giving it to him if he asked... then only at home, not outside, etc., and only for sleeping/naps. Then, one day we told him we had to collect his Binkies for Santa... who needed it to help other children. He actually helped us gather them up... and then we put away the bag. Out of sight. (I still kept it as a "souvenir").
For us and my son, this worked. He took 2-3 days/nights of asking for it.... and taking longer to settle down and fall asleep... but he did not have angst nor did he get fussy or have tantrums about it. He did ask for it... but we repeated the "Santa needs it..." story to him. And he was satisfied with that. But I also co-slept with him to help him adjust.. and he'd ask for me. I have nothing against that.
I did before, try the making a hole in the Binky tactic and using the making believe its lost or "broken" tactics... but for my son this did NOT work... he would then just tell us to go to the store to get more... because "the store has Binky..." he would tell us, or whenever we were at a store, he'd go to the Binky aisle and point to it and tell us to buy one. So that tactic was moot.
So, there are many different approaches. But mainly... gauging your children. Then seeing if you indeed DO want to get rid of the Binky, absolutely, right now. Some kids wean from it on their own. Some don't.
Again, I think, just using it only at bed/nap times are not much. But I know each Mom is different.
For my cousin's twins... their daughter heard them discussing it with the Pediatrician (in front of her)... and then when they went home, their daughter just threw it away. Just like that. And that was it. She just stopped using it, after hearing the "Doctor" giving them suggestions about it.
Parents either do it cold-turkey or gradually. The tactics vary. There is no one single way.
And yes, my son also has a dear lovey he sleeps with too.
All the best,
Susan