My DD was 11 when she asked me how old she had to be before she could have sex. (yes, we had had 'the talk' as she had hit puberty by then)
Without taking a breath, I immediately replied "35". We had a giggle, and then talked seriously about it all. I informed her that the legal age was 16, but that in my opinion it came down to not age, but maturity. We talked about all the other stuff that comes with DTD. How it's not just all the fun and excitement, but the responsibilities that go along with it.
When you can comfortably and confidently say no as well as yes.
When you are mature enough to go see a Dr about birth control.
When you feel comfortable going to a health clinic to get STD tested.
When you could cope with being a parent. etc etc
We talked for hours over the next few days, and then she dropped that subject and started on global warming, or anti smoking, or something else of lesser importance than sex. (joking)
Over the years, she had many, many friends stay overnight. Both boys and girls, in groups or one at a time. Our home was always full of teens, and I always made them all welcome. (maybe because my friends never were)
She met her "first" when she was 16, and they waited until she was nearly 18. My point? Not sure really, but sleeping together isn't always all about sex.