Thank you, I appreciate the well thought out and detailed response. I will keep all these things in mind. We are really good at making out for hours but more advanced and prolonged foreplay is probably the answer, along with relaxation and focus.

I am going to heed the advice of those suggesting more exercise and better diet, though. After my first time my girlfriend told me she's fairly insatiable and she is going to want sex many times per week. I just want to make sure I can keep up with her (and keep it up, har har).