It depends how old you are, and if you both drive.
When we were young(er), we would go to Colorado non-stop, about 32 hours. But we were usually so tired it took a full day to recover. So we don't push it any more.
9 to 10 hours of actual driving will equal around 12 hours total, which is long enough. We try to stay at campgrounds, as there are lots available. With the economy the way it is, crime seems to be an increasing worry, and I have heard of a more than a few campers getting robbed at WalMarts, a few ending up getting killed. I'd rather [pay a few bucks and feel safe.
Also be careful at rest-stops, especially at night.