I want forever in a marriage; well until death do us part. That isn't really forever, especially to someone who thinks he's got an immortal soul, but I think it's what is usually meant in romantic references such as songs. A lot of people think that wanting forever is the mark of a hopeless romantic yearning for the impossible. I'm going to be a little blunter than usual; they are wrong, there is plenty of clear evidence to the contrary. Marriage for life is still the norm in many parts of the world, was the norm in this part up until recently, and is still not all that uncommon here. And the people who engage in it, and the way married parents in those places/situations encourage their kids to marry, say they think it works pretty well.
Now, in some of the cases like marriage in India, where about 90% of marriages are arranged and there is almost no divorce, there are factors that help with that. One is clearly defined and socially enforced gender roles. A closely related one is limited expectations. The man does X, the woman does Y, and if both X and Y are kept up divorce is unthinkable; if they are not kept up the man or woman who doesn't keep them up is deeply shamed. X and Y are both quite doable and both viewed as sufficient. These two factors (enforced gender roles and limited expectations) obviously have their own cost; the cost of the first is basically the central point of many of the blogs I read.
One of the costs I guess at is a male-initiated sex life. In an Indian marriage, I suspect the man gets as much sex as he is willing to demand and argue for, and the woman gets as much sex as the man asks for. I have the impression that if she wants more she's basically expected to dress up and act sexy and try to get him to ask. I did agree to always be the one who initiated when my ex requested/demanded that after we were already married. But it's absolutely not something I would agree to from the beginning. It's a cost I'm not willing to pay, but I don't think it's required.
Another cost I guess at is that adultery is both fairly common and hypocritically vilified; winked at sometimes in private, loudly denounced in public. One of my coworkers apparently went to bars to pick up girls regularly while he was living here and his wife was living on the other side of the country. Cultural rules differ vastly on body language but another coworker, who spent the week near work without her husband and the weekend with her husband in another state, tended to look at me in a way that if she were American I would have considered an invitation to ask her out. (And boy, was she cute, so being eyed like that was kind of fun.) Another cost I wouldn't agree to from the outset, though not as bad as the "always-initiating" one in my mind.
I think there are things we can learn from other cultures, both in terms of what to do and what not to do. The thing I think we can particularly learn from in terms of what to do is limited expectations. There's a lot in forever that I would agree is impossible. It is impossible to keep the same kind of romantic feelings that sweep us off our feet in the first few years. Your spouse is only human; there will be mistakes and failures. And the main summary one is, your spouse will not, cannot, and is not responsible to, make you happy. Your spouse can and should be expected to do lots of predetermined things for you; but it's up to you to be happy with them.
I guess what I want is someone who will always love me the way I intend to always love her; love as an action, a decision. The earth from which all kinds of romantic emotion can spring. I have some record now of loving my exes despite poor treatment, and always trying to make it better. I want someone who will treat me the same way; who will always listen and try. Who I can be confident will keep trying to love me as I keep trying to love her, all our lives. And I don't think that's impossible; and I think that is love forever.