It seems impossible to find out the best answer to this question.
In my opinion, to discuss this topic, we should make a comparison between 2 countries, 2 regions or 2 classes.
So, could you please give me your ideas to make it more simple to deal with :)
What do I think about a trial marriage? I think marriage is less like a trial, and more like a sentence.
I think you should live with someone for one month, then change partners, and continue this pattern for at least a few years. Now if I can just convince some women...
I think it's very usefull to try living together before real marriage. But it shouldn't be too long, 6-9 month, not more
In the United States attitudes toward sex have changed a lot, and they have swung back and forth over the years.
During the 1950s when I was growing up, the United States was very prudish, sex was not discussed openly, homosexuality was actually a felony (serious crime) in some places. Fornication (sex between unmarried single people) might or might not have been against the law, depending on what state you lived in, although the law was rarely enforced.
One always has to be careful because there are always differences between
a) what HAPPENS,
b) what is APPROVED OF, and
c) what people are willing to TALK ABOUT.
For example, from 1930 to 1968, U.S. movie studios followed a very restrictive code, and in U.S. movies made during those years, even married couples were shown as having bedrooms with two separate twin beds!
Public attitudes in the United States underwent a change in the late 1960s that was referred to as "the sexual revolution." The contraceptive pill was an important part of it.
I'm not sure that the actual behavior of young people changed all that much--couples have always "shacked up"--but in the 1950s they would have hidden it. They might have told a landlord they were married, and the woman might have bought a cheap fake wedding ring. Very likely the couple's parents would have known what was going on, but would not have been willing to express approval, and thus might "turn a blind eye" to it--just pretended it wasn't happening and not talked about it.
In any case, modern sexual attitudes in the United States are a relatively recent change--although as I say the pendulum has swung back and forth.
In the United States I have never heard of anyone talking about a "trial marriage" in the sense of any kind of formal arrangement by that name.
It is very common for a couple to live together for a period of time before getting married. My wife and I did that--forty years ago!--and I personally think it is a good idea and good plain common sense.