Many people say now that you are silly if you do not live together before you marry, because then at least you see your partner as they really are. its an intellegent argument and makes a lot of sense, but the proof does not really seem to be borne out in society. People who live together first have higher divorce rates then those who don't for example.
Personally I did live with someone and then married someone else. I have always said that there was no comparison between the two. I came across this article today which I think is interesting.

Cohabiting couples destined for singledom

Weston told the Sydney Morning Herald that many young people thought moving in together was "a fun thing to do".
But she said cohabiting couples often lingered for years in unsuitable relationships and had trouble finding new partners when they eventually did split.
"In the old days people might go 'steady' but there was still opportunity to meet others," she said.
"Now once you are living with someone you are cheating if you see someone else. When you cohabit it adds a sense of commitment to a relationship that might be going nowhere."
Weston told the Sydney Morning Herald that cohabiting couples in the 1980s had tended to treat the relationship as a trial marriage and usually went on to marry each other quickly. "Some might have separated later," she said.
Now, many people enter relationships before they are committed, and without having discussed their future.

"They enter prematurely but can linger on and waste their time," she said.
read the whole article here