Depends. Since we work and have a kid in school, time is critical. Going to Fl from MD as an example, I will try and do the drive in 2 days. SC, I might stretch out one. Given a preference I like to be around 4-6 hours and can usually stick to that on most of our trips, but longer, destination trips I will get plenty of rest the night before and do longer stretches - maybe up to 8. Any more than that and it's stops being fun. That said, I have planned on long days and stopped for the day ahead of schedule if I was getting tired. Getting there on a planned time is one thing, getting there in one piece is another. The safety of my family and others is far more important than meeting a deadline. My thought, have a plan, try and stick to the plan, but put in a contingency stop if I get tired en-route. DW doesn't drive, if she did I could see us doing longer stretches. I don't mind though, I like to drive. I do take breaks about every 2 hours to stretch, fuel up, etc.
If I were retired I could see throwing a plan out the window and drive and stop when I wanted. But in our current situation, I try and maximize destination time.
