OK, first question--How old are you?, and second question--How long have you been seeing your significant other? The answers to both are going to weigh heavily in how I respond to this.
Maybe cuz I'm not a guy, my answer doesn't 'qualify' in this conversation, but what the hell, I'll put in an answer anyway.
I'm 27 and have to agree with Chaos. I've been with Brian (32) for about 4 years now (I know, still relatively short period of time) and both of us are in love with each other and don't want to sleep with anyone else, hence one of the reasons we have for getting married. For reasons I refuse to get into, I do know that this is a fact about the way he feels; it's not lip service on his part, so to speak.