Maybe it's because I was a teen during different times (I graduated H.S. in 78) but I grew up with quite a bit of freedom. On weekends friends (mixed group) would hitchhike into the big city to go to concerts and the summer I was 17 I went to NYC with my then boyfriend to work for the summer and save money for college. We lived together with a group of other people, not so much to "play house" but because it was economical. This was before computers/cell phones etc... so I called home once a week to let everyone know I was fine. I worked 2 jobs, but yeah - there was still time for fun and games -that's what being a teenager is all about. I managed to graduate from college (which I paid for 100% myself) and because of my experiences as a teen I've always been very independent.
No, I didn't end up married to the person I spent the summer in NYC with, but I have great memories of a great summer where I learned a lot and grew a lot.
Maybe I have a different perspective on this because I had a great experience with trial runs of independence before I hit 18. Or maybe the reason I have a different perspective is because I have a different attitude about sex. I see so many on here getting hung up in the sex part of the couple going away for the weekend. That, to me, is the least of my concerns. I'm more concerned with can the teen afford it, do they have a back up plan in case something goes wrong, are they usually responsible and so on. To me, a 17 (almost 18) year old who is in a long term relationship having a sexual relationship is not the end of the world. It wouldn't surprise me, and it wouldn't concern me. I wouldn't have a problem with it at all.