Short answer is till I get where I am going.
I don't have enough vacation to take a day off for a travel day.
Plenty of days of wake up at 5am drive 85 miles to work (yes that is my one way commute) work till noon and leave early. Drive 85 miles home and switch vehicles. Drive 500 miles and setup about 11 pm to be ready to go off roading in the morning.
When I am retired or if I had more vacation no way in the world I would do it this way but right now it is how it is. If I had unlimited time I would probably do a couple hundred miles a day if I had a destination I was going to.