Yes, people have expectations and standards. Those are going to vary wildly from individual to individual, but probably with some common themes.
Yes, I think shared values and goals are also important, and you can lump that under standards/expectations.
Mutual benefit is very important...but I'd say that a good many people stay in a marriage even when the benefits are largely running one-way... the other way. I've seen it many many times. Why do they do this? Sometimes it is out of love for the other person and hope that things will change for the better. Sometimes it is "for the kids". Sometimes it is out of fear that leaving the person would end up worse. :shrug:
A rope that has more strands is stronger rope than one with few strands. Relationships are also like that; the more ties and shared values/norms/goals/expectations/wants/needs/hopes/dreams/etc that you have, the stronger it is likely to be.
I personally think that one of the big ones is a belief in something larger than yourselves. A common shared belief in a certain religion seems to help people make it through hard times and maintain their marriage. Belief in the sanctity of marriage itself is, IMO, a big reason that divorce used to be rather rare. Raising children as the next generation of humanity can be a shared value that transcends mere self-intrest also. There are other possibilities, like a couple I knew who spent most of their first decade together serving as missionaries and aid workers in poor nations.
My own expectations? Well, that could be a long list. Shared values: similar religious beliefs, similar morals, compatible "pace" and many shared intrests. Agreement on children and childrearing issues (although I'm almost past the "children" issue and approaching the "grandchildren" phase, lol). Some degree of intellectual parity. Monogamy, honesty, respect, companionship, mutual support of our shared prosperity. Doing many things together, but not being adverse to spending some amount of time apart each week (ie not needy or clingy). Someone who likes to "go and do" and have fun, but who can also enjoy a day spent watching the river flow past.
Well, I could go on at some length but you get the general idea.
The most vital ingredient is love, however. Love alone is not enough, but without love nothing else matters as much. When I say "love", I don't mean infatuation, lust, or simple emotion. I mean a devotion to the other person that surpasses reason and explanation, where the other person's happiness is vital to your own. Emotions come and go, wax and wane and wax again... true love is a committment made willingly.
