Well I thought I should just list what I think how it goes for the relationship stages.
Dating go out get to know each other, still open to date many people, exlcusive dating basically getting the bf/gf title, spend time together but still don't live together, moving in together adjusting to sharing a home with a person, now i personally would stop at this one and would never go to marriage but maybe open to children at this stage.
Finally marriage, you now have to deal with people in the marriage state of mind. Which is basically no matter what I do you wont leave me so I can do whatever I want. Not to mention if they observed their parents being married then you may have to deal with that emotional baggage appearing because they observed a certain kind of behavior and it may seem perfectly normal to them.
As far as the religious way of thinking of friend to marriage I find it illogical to just jump into something when in stages you can seperate the problems that come with it over a course of months or years. And reduce the many problems that come along with each of the stages. Like jumping over hurdles on tracks. If you just jump into a marriage its like trying to jump a mountain and unless your a super person and your with a super person your going to have a hard time making it over all the problems. And its little things that destroy marriages something minor that is just done repeatedly. Then it can spread unless the other person becomes okay with it, or you change for them.