This is making me think. Sounds like how long we have been using them is unusual. We still use the cr*ppy BT ones for both kids (sound only) and they are 4.5 and 2. It is just part of the routine.
The problem is in our house we will not hear them without the listener on the rare occasions when they get upset in the night.
But I do want to stop using it for the older child but he wont like it and I would prefer he didn’t get out of bed if he wants something as it may be tough to get him back into bed. However, I think it is time to bite the bullet on that. Conversation with the wife this evening.