Miles per day?

I would suggest that the answer depends upon your tolerance for mind and body numbing WORK. Mine is low, so I shoot for driving about 6 hours a day tops, which usually means somewhere around 250-300 miles. I can do that every day for a couple weeks. More than that gets me burnt out after the second day. So the question you have to ask yourself is whether you mean this trip to be a (painful) forced march, or a vacation. If the former, heck, 500 miles a day will get you there in a mere 4 days, and you can then collapse in a smoking heap. Or, take 8 days, admire the scenery, stop for roadside attractions of interest, and arrive ready to partay.