When should teens to go bed?

[Rodion15]

I’d like to hear opinions from other parents.

We’re a married couple. We’ve got three teens of 20, 15 and 15 years old (twins).  We’re constantly having issues with them staying up and talking till 2am, 3am, if you let them on…all night long. 

We like to be as flexible as we can with our children, but if we allow them to stay up late, they get used to it and get too noisy.  We explain the whys again and again but they won’t give up.

I sometimes think, what if we’re being too strict (mostly I, my wife just gets really annoyed on and off, and when she does, she really gets annoyed). 

I’d like to hear experiences on this (without condescending advice please!).

[blueskies]

I have a good relationship with my children (aged 13 and 16) by good relationship I meant they dont fight me on rules too much and we have always given choice and negotiation. Sleep and healthy main meals I've always been little tougher on with negotiating.
Many of my friends struggle with telling their kids past about 11yrs old to go to bed before they do.
My kids usually shower an hour before bed and following this we do not allow tv, devices, etc 30-60 minutes before bed. We have tried sooner but they actually just take longer to fall asleep. 
We occasionally have patches where they don't sleep....our rules is no devices in the room unless its just for music. If they have longer patches I will ask them to come for a walk with me after school pick ups.
I offer what ever they need in their rooms (books, diamond puzzles, gadgets, different lights, etc.) to have them kill a bit of "down time" before bed. 

We enforce 9-10 hours of sleep a night (sometimes a touch more) in our home. On weekends no less than 8 hours.
During the holidays we are pretty relaxed (but wake them after a later night to keep them around the 10-12 hours sleep mark). As we get closer to it returning I slowly wake them earlier and earlier so its not a shock to their body clocks getting back into their "normal sleep routines".

[Rodion15]

We usually have long conversations with my offspring explaining the whys and trying to encourage them not to get hooked to screen devices, trying to read a little, keep their room tidy etc.  I am under the impression that parents don't always tell it around if their children rebel or are unwilling to submit to any reasonable rules.  This is a sensitive issue too, as nobody likes to be taught on this or be talked condescendingly.  

Thanks a lot for your answer.