I know of people who had known each other for just weeks before they got married, and they're still married today.
However, I do not agree with cohabitation before marriage. Maybe I'm old-fashioned and you can call me whatever you want, but I was not raised that way and to me, it doesn't look right. Plus, what do you think is one of the top 10 reasons why men who have been living with their girlfriend for more than 5 years won't just marry them already? Because if they can live with their lady WITHOUT getting married, they aren't gonna rock the boat.