Do you have kids? how old are they? Do they travel well? What time is the flight out? How many tickets are you purchasing.
3 hours there and back is six hours of your time. For us, I wouldn't do it if the tickets are free. We have two small children who don't do well in the car for three hours, we like to take the early flight out, neither of us likes long car trips, and the extra sleep is worth something. And my time and gas are certainly worth something as well.
Now, if it were just me and gas was free and I wasn't flying out until late, I'd do it to save $30.