Welcome aboard, Nanners Mossman
! From what I hear, Arizona gets pretty cold at nights. If it gets below 50 degrees F, the banana plant could go dormant. I always dig mine up, pot them, & bring them indoors before that happens. If you have winters as cold as central Oklahoma, ya might wanna do the same. I have 4 nanners inside right now. 3 are more than 8' and my plantain is about 7' tall. They all have yellow leaves (normal for fall) & so do my Elephant Ears.
Think Sbl's right about the "shorter days" thing. He's also Definitely right about the water thing. Cold + water = corm-rot.
It's a very friendly & info-packed forum so you'll definitely wanna do some more reading before ya decide. If ya have any questions about using the forum, just ask.
Enjoy!