870 miles, close to 14 hours-For every trip to the World, I have driven so I'm pretty used to the drive. Plus, the gas money is about the same as 1 plane ticket so with 4 of us, we save a lot!
I live in Austria and it takes us about 20 hrs, too (including a lot of waiting time in Frankfurt), I just looked it up and for us it's 5101 miles. Might be a little less for you, but not much.