You'll never know for sure how durability will really turn out until you actually try it in your climate and your situation. Some things can be estimated by finding others experiences in similar conditions and usage but that's still just an educated guess.
We have 3 cars with considerably different usage patterns; all protected and maintained with same set of products/coatings:
1. Car 1 will likely get to 3 years (if not longer) before needing to be completely redone.
2. Car 2 will likely never need to be redone.
3. Car 3 will get to 2 years at the most before needing to be redone.
1. Car 1 is about 5500 miles a year, no freeway, sits outside from April thru November but only really driven daily November thru April, short trips, no freeway.
2. Car 2 is daily driver in nice weather, April thru November, usually no-rain days only, always garaged, 5500 miles a year, rarely freeway.
3. Car 3 is year round daily driver, generally always garaged, 25k miles a year, 95% freeway.
All are in NE Ohio.
Same protection, varying usage far different likely outcomes. Freeway use, especially during winter, is very, very hard on a vehicles finish.
Having seen a lot of faded cars last time I was in Arizona, I'm guessing they have a whole different kind of nightmare to deal with, entire different set of circumstances to cope with. Florida apparently has acid-filled Love Bugs that can etch paint if left for too long...another nightmare entirely.
Point being, no claims listed on a box can even begin to adequately predict longevity. It's the ultimate YMMV scenario.
I have got a pretty good idea of what works well in my environment, both on well maintained and not-so-well maintained fleet vehicles. I've got some fleet vehicles that are still doing well after application in 03/2017 and some that didn't make it thru 6 months of fleet use. There are things out there that will meet, and in some cases likely far exceed, your expectations...ya just gotta find what works best for you in your environment.