I'm actually a new user, rather than a Rachio employee. It just seems that there aren't as many of us desert dwellers, so the peculiarities of desert watering makes us jump through hoops. I've gone to this website for some guidance on watering in Phoenix. Under the interactive guide, they list this first.
With the # of emitters and associated flow rate for each of them, it translates to recommendations of 4-8 hours of watering at a time, every 10-12 days. That happens to be the interval that the 'As Needed' schedules are showing, which is great, but the duration that I can set per zone is currently capped at 3 hours. The Rachio guys are still trying to address that, and I'm sure they will. I just wish it weren't so complicated to figure out how to optimally water in the desert. The above website is great, but to date with my old Hunter Pro style timer, I've had landscapers water at much different intervals. I don't necessarily trust their settings, as I think they have a tendency to over water, but now trying to figure out what is 'real' is a challenge. Thanks for providing info. on your situation. I might try to start a 'Desert watering' thread to see if there are enough of us out there to share our Rachio settings on Flex, Fixed or As Needed to make sense of it all.