About Relationships and the "Norm"?

I've always felt that with romantic relationships, what happens HAPPENS, and that people are just supposed to move with the flow- let nature take it's course, and all that. I'm not a hippie or anything, but romance isn't something that can be monitored... right? Well my boyfriend's mother has this ingrained belief that at a certain age-we are almost 17- you aren't supposed to be sleeping over and be so involved with one another. Yes, normally 17 is not a very mature age, but I think in some cases, people truly do find someone they love and WILL love for the rest of their lives. I am not going to say that I'm fully grown or whatever because that would be untrue. I know I still have a lot of maturing to do, but I don't think that I should stop myself from going "in too deep" when I'm already immersed. Another problem is: I don't feel comfortable around my BF's mom, so I don't go over his house often. I don't want to be offensive but I really don't want to go. What should I do?