My kids have theirs in their rooms and all the time. They have learned (trial and error) how to handle it themselves at around your kids' ages.
They've made mistakes and learned the hard way - but have learned. They also pay for their phones (work) and so it's all been a part of it. They have stayed up too late, and been exhausted before. They were on too much and didn't do test review. It's only happened a handful of times.
I'd rather they figured this out now before it really matters - and when they can catch up. That's just the way we've handled it. Small mistakes, and we go over it. Mine are not addicted to them though. I think it would depend on your child(ren). If they show responsibility and can handle it, try it. You can always do a test run.
ETA - for us, there's also Netflix, tablets, computers, .. other devices .. so more important they learned they have to be responsible to get up for their early morning hockey practices, and work shifts (fast food), etc. That's on them. We won't call their managers.
When hubby gets in (sometimes works late) or goes to bed last, or I'm up - those devices are all off - for us, it was more when they were younger (like junior high) that we had to worry about them being up all night, and we did monitor it then.
ETA 2 - I saw your new question (which I agree, you'd do better to add as SWH here and add that to your title of question so people know you've added one).
As for as renegotiating - I don't think you need to, especially if they aren't asking. When my kids were young, I didn't do 'limits' on devices. I just knew when they needed outside time, or time to call up friends .. much as my mom did when we were growing up and were watching too much TV. Sometimes I think we overcomplicate this stuff.
If your kids don't have them in their rooms at night, that's absolutely fine. Here's what happened to us when our kids first had them in their rooms at night - their friends who had absolutely NO control, were texting them all night long. They were up at 2 am playing games and would want my kids to go on and play Clash of Clans or something. So my kids learned to put on Do Not Disturb.
The kids who were up at 2 am playing Clash of Clans? Were the kids who had a 1 hour screen time limit and were up sneaking their phones in the middle of the night.
I just let my kids have some responsibility in spurts. I don't think you need to overthink. If this is working, and they are not asking, I would not overcomplicate.