What keeps relationships alive?

This is a concept I've been thinking about for quite some time, but just haven't been willing to communicate my ideas for one reason or the other. Perhaps this is because there is an infinite amount of answers to this question, or least it seems so.

What keeps two people together? Is it the constant, trivial annoyances brought forth by the guy? You know what I mean. I see this shit all of the time. I'll be at a party or a get together of some sort, and most everytime I've seen the boyfriend acting like an ego-tistical jackass just so he can appease his friends and give the party entertainment. His girlfriend is the sacrifice and often enough the butt of all of his jokes. And although she is aching to slap the hell out of him the whole time, it makes her want him and desire him even more then before. This ongoing process is something I have seen in relationships and social interactions, and although it could have detrimental consequences and a cause a serious blow to the relationship, it seems to carry out the relationship for an extended period of time.

And why is this? I mean I've seen/heard some of the most cruel jokes from friends/enemies alike, and it seems like the girl is mad, but she simultaneously likes the fact that the guy is getting underneath her skin. Maybe this is a key-concept in keeping a relationship together. Sure there has to be physical affection and some kind of emotional lovey-dovey connection, but to keep the relationship heated and going - something has to fuel the fire, right? Is it possible that many women enjoy the drama and enjoy this kind of treatment? I am sure there is many girls who would vehemently dismiss these claims, but there is tons who love "the asshole kind of guy."

Now this plan seems to be very common in most all relationships I've seen. And what is the common result? Failure. This isn't because the guy goes over the line, but its because the guy has nothing else to offer. Sure he may give her a good fuck, or maybe he spoils the hell out of her, but his routine gets OLD. The girl gets tired of it and wants something new. She wants a new spark. The guy may continue to be a funny asshole, but the girl is probably getting tired of it and realizing how lame it is.

This is just one of my many thoughts on relationships and what people do to keep them alive. I'll write more later on, perhaps on what a girl may do/not do to keep a relatioship going and why the GUY gets tired of it.