The best option that I've ever used for multi terminal connectors are GM WeatherPack. You can get them with pigails to solder or crimp on, or they come in kits with terminals, seals and connectors.
I've used Napa's Solder Seal, heat shrink connectors and they are pretty decent quality. They also have a crimp and seal connector that works pretty good too.
Actually, a standard crimp connector should have a better lifespan in the AZ heat because of the low humidity. In my experiences, corrosion causes a lot more connector failures than heat.
If you are using quality terminals and zip ties, they should last quite a long time. I've used 1000's of both subjected to under hood temperatures nearing 300 deg F + with minimal problems.
My pickup still has all of the cheap connectors on it that lived through 4 years of AZ heat. And that was almost 15 years ago. Looking at the snow on the ground and falling outside, kinda wish I was there about now
Jason