So, the good thing about Fort Davis is it's only most of the way to Big Bend. It is a really long drive - and while there is a beautiful back way (on US-67), the Interstate is just faster - which is the point of the Interstates.
If I had the time, I would find a halfway point, and do a two-day drive on US-67, but we didn't for this trip, so I-20 it was.
Last time, we did the drive to Marfa in one day, I swore I would never do it again. However, much like the people that always fly in to their cruise the day they sail, sometimes, time just gets into the way.