It's pretty common for sex to slow down a bit after that inital "honeymoon phase." But in a strong, healthy, long term relationship, that phase should last anywhere from 1 to 3 years. My boyfriend and I have been together a year and a half, and even though we have our days/weeks where things aren't too crazy, because we both work a lot, etc, we do still have a very passionate sex life. We are spontaneous, passionate and sometimes even freaky. Also, has she recently started taking birth control? When I went on birth control it lowered my libido a lot! I noticed and hated it, so I got off it, and things are back to normal!