I moved from sunny Dana Point, CA to the Chicago area in 2007.
This was after a year of us flying back and forth to visit one another every month.
The only reason I relocated or would advise another to do so is if they plan to get married. We were already engaged by the time I moved out here and also had put down a deposit on the reception venue for the following year. I also grew up in the Midwest as a child and still have family in nearby states. Still I do miss those 80 degree February days in California! :-)
If you aren't engaged or have plans to get married then it's hard to justify leaving the life you know just to be close to someone you're dating at the moment. The only exception is if you hate the town you live in anyway, your job sucks, and you have been thinking about making a change anyway. Just make sure when you move it's "not for someone else" but rather it's because YOU want to relocate!