G'day Paul, welcome to the RTA forums !

It's a full 3 day drive from Phoenix to NOLA so with 13 available, you have plenty of options to choose from while driving just 4 hours a day. You don't say whether or not you return to Phoenix in the second half of your trip or what you plan to do, so it's a bit of a guessing game. What I would recommend you do is look north of Phoenix and into the 'Four corners' region [AZ,UT,CO,NM ]and although it doesn't fit with Roswell and Tombstone, you have the likes of the Grand canyon NP, Monument valley tribal park, Arches and Canyonlands in UT, the Colorado National Monument and the spectacular Million dollar Highway [US550] with the small mountain towns of Ouray and Durango in CO, Santa Fe, Albuquerque, or even stay north for longer to Colorado Springs. This is just a few of many so I would suggest you study a good map and do a little research and see what appeals to you, once you have a few more dots on the map we can make more meaningful suggestions.