First time, we didn't live together. Second time I got married, at least we knew each other as friends for many months, but still didn't live together.
A longer dating time is a better idea than anything. Sudden marriages, like my first one, is kind of risky, but not always a disaster. We all know exceptions like two 18 year olds who got married via an arranged marriage and stayed married for life. It happens, but probably rarely.
I think living together is a better judge on if you can last through marriage than dating, my wife and I only dated about 6 months before getting married, but lived together just about that whole time, but I suppose I am one of the exceptions, got married at 18 and our 6th year anniversary is 4/20/09