>>212541547 (OP)In my experience, you find out whether a relationship will work out for the rest of your and you partner's life around the 10 year mark. If you spent a decade together and there are no visible cracks in the relationship, you're probably good to go till one of you dies.
The issue is people don't get married after a decade. They get married after a few years tops, then the cracks do start to show up after a decade, but you still stay together because marriage/loans/kids/etc., then after another 10-20 years one person has had enough and divorce happens.
The lesson? Don't rush into marriage. And if you did, do rush into a divorce if it's not working.