Pretty sure after about 6 months asked the question at the about 2 year point, was about another 3 years till we both were out of college. Married shortly after she graduated and it's been just shy of 29 years.
I think too many folks fall in lust and not in love and jump way too fast. It takes a while to find out if all the other things that need to mesh mesh. To be blunt, just both being whizbangs in the sack, on the sofa, in the kitchen, and car ain't enough.
Like it or not you are marrying each others families, political views, hobbies, interests, etc. There is a hell of a lot of stuff that builds and makes the whole person, and if the wholes don't mesh, you likely aren't going to make it. People don't change all that much after marriage and going in ignorant or hoping to change things is not predictive of long term good times.
For example say you like guns and dogs and hunting, and after a whirlwind romance, you get hitched. In 6 more months, you tell her "deer season starts in two weeks I have to get my stand and scent," and she says "WTF you can't kill a deer around me you brute!!" It's a little late to find out then that she tolerated the guns and a little range time but she comes from a family that has hated hunting since before she was born.