Is it important to keep your virginity as long as possible or this just a sexist notion?
Yes, It was and is for me. I think the key is similar to what Onyx said in that it should be with someone who is not only special to you, but someone who considers you to be equally special. It should not be something you are pressured into or with someone you later regret. I was 19 and it was with someone I had been with for years before and after that, and even though we are no longer together, I have no regrets about it.
I will encourage my future daughter to wait, but I will be honest with her about my own decisions. AND MOST importantly tell her that just because she is no longer a virgin that that doesn't mean her body is still not sacred or precious; that she doesn't have to give it up automatically just because she didn't wait until marriage.
That's great encouraging her to wait but its going to be one helluva challenge for you both. Kids have access to sexual content 24/7. Also the music and music videos are laced with sexual content and lyrics. Then the natural progression that couples follow as the relationship blossoms and kids living as if there is no tomorrow. I sincerely wish you well.
I think that is where firm parenting comes into play. Parenting in and of itself is a "helluva challenge". Sex is everywhere, so is drugs, crime, abuse, etc. Sure you can't stop them from seeing everything, and you shouldn't, because sheltered children are just as bad as those with no restrictions. It's about creating and maintaining an honest dialogue with your children-not being friends but being present, listening, and being rational, in addition to being a good example. Of course I will encourage her to wait until she is mature enough, ready enough, and knows enough, that is my job.