What part of Arizona? I have family in the Phoenix area!
My DD is now 9.5 WO, but when she was 4WO she slept a lot! She was pretty easy to keep on a routine at that time, but she would take 40-45 minutes to eat and then a quick diaper change and back off to dreamland. There's a post on the General Sleep Board that has the awake/sleep times for babies of various ages, but I found that my DD has always slept more than average.