The bases arent a recipe, its a form of comunication. How far you got with someone. Somewhere along the line of growing I concluded that maturity and popularity was linked with getting to this or that base. I like however the comparison between age and a base limit. The consequences for error could lead to disease, unwanted pregnancy, abortion.
I think the emotional impact of intimacy is beyond what some, if not many younger persons can easily cope with, and the pain of separation may be less devastating for an older person. Your going to have to know yourself well enough to know what you are going to do, and be responsible enough to face the consequences. I try to avoid telling them what is right. Instead I tell them that this is the ultimate puzzle anyone must solve. In the end we all chose to do what we think is right, and this defines us.
I think this way, because as I grew up, I became fiercely independent to the point, that anything my parents would say, I tried the opposite. So what age is a good age for intimacy? I think the psychological risk of harm is less above age 16, and really should not be pushed at any age. I think a very safe age is when you are an adult, then it is your life, your body.
You still by the way, will have adult responsibilities. Also there are some who will have difficulty with intimacy at any age without therapy. It pains me to recollect all the things I did in youth. I would be worried if my own kids followed my slutty ways. Love, sex, so much better when they are the natural evolution of things with someone you love, shared at a meaningful pace.
I can say that after 18 years of marriage. On the other hand, I was one of the young ones running up and down the street when I was young.
My discussion above is a purely pragmatic approach practical reasoning with touches of practical morality. Sex and ethics go hand in hand.