AGM batteries and high heat

(as not to threadjack a post in the GRM forum)

Las Vegas is he|| on car batteries. Parked in the sun, a battery can be sitting all day at 140F+. Having a battery last 3 years is virtually unheard of here. In fact, I replace my battery as a matter of course every 3 years - when they die, they die hard, and I can't afford to be stranded.

Wondering if the hive mind might know if an AGM battery might do better in these conditions. Quick Google research suggests I might be able to use a Miata-style battery in place of the Group 25 in my Scion.

Any info greatly appreciated!

AGM = Air to Ground Missile in my world.
Die Hard. Nice. My last battery failure was like that. A quick trip across town. Return to my car an hour later and find a dead dash board. No warning whatsoever. Made me think of buying one of those portable charging stations (wow! car vocabulary failure). I don't know if that's more cost effective than changing batteries before they fail.

I know that AGMs do not like High heat.. not sure that 140 degree temps qualify, but I know the one I had in my BMW 318ti died a horrible death after being put into the stock location which is next to the head on the passengerside and over the exhaust manifold.

The same battery lived quite happily in my old Hyundai Tiburon, and it was behind the passenger side headlight, but still in the engine compartment.