I think it is very helpful to learn about the person that you are about to marry. It takes many years to know everything about a person and in some cases you may not ever know everything, for some people may not tell all of their past for the fear of lossing their future partner in life.
But, yes it is very smart to date, even if it takes years before you marry especially if you are not completly sure if this may be the right person you want to spend the rest of your life with.
I shouldn't talk to much about this because I dated my wife for 3 months and married. This May 2012 we will be married for 31 years !!!! So all people are people and relationships are tatally different.