My reasoning for my guess - Well once you leave Scottsdale you will have to stop by Cigar King for one last smoke. Already you are now an hour behind. Next you will have to gas up in Palm Springs; as we know, you cannot pass up Fame Tobacconist with their awesome prices. I say spend 2 hours there. Last, you MUST stop at Morango for a few hands of poker. Now that you have spent 4 1/2 hours off the road, the rest will play itself out.. good luck and have a safe drive.
By the way, I really recommend you follow my driving instructions above..
Rich