Looking for happines in marriage survey according to living/not living together before marriage Do you know any research/survey results comparing how happy do people feel in marriage (after a few years) comparing marriages who lived together before marrying and living separately? 

There are many studies into comparing divorce rate among spouses living or not living together before marrying, but I think it has a serious flaw - religious views can make couples still live together in marriage even though they feel unhappy. I think feeling happiness could be more interesting statistic.

Is premarital cohabitation associated with later marital satisfaction?
A study reported, in the 80's, that unmarried cohabitation prior to marriage was associated with &quot;significantly&quot; lower marital satisfaction, but did not report an effect size. They also reported that the duration of unmarried cohabitation was unrelated to marital satisfaction(DeMaris and Leslie, 1984). A later study by the same lead author from the 90's reported that unmarried cohabitation predicted later divorce after controlling for time in union (DeMaris and Rao, 1992), which I include because time in union could be a confounding factor and I could not find direct evidence.
Wydick (2007) gave a game theoretic account of why unmarried cohabitation may lead to relatively decreased marital satisfaction which I am not qualified to evaluate, but the paper cites a number of empirical studies that support DeMaris' older thesis, so this paper may also be of some interest.
Not to speculate, but this is subjectively surprising to me. When I began the literature search, I was confident the idea was nonsense, and yet here we are.
References

DeMaris, A., &amp; Leslie, G. R. (1984). Cohabitation with the future spouse: Its influence upon marital satisfaction and communication. Journal of Marriage and the Family, 77-84.
DeMaris, A., &amp; Rao, K. V. (1992). Premarital cohabitation and subsequent marital stability in the United States: A reassessment. Journal of Marriage and the Family, 178-190.
Wydick, B. (2007). Grandma was right: Why cohabitation undermines relational satisfaction, but is increasing anyway. Kyklos, 60(4), 617-645.