This may not be worth the trouble but if you have a small 12V battery like for a motorcycle or garden tractor, etc. if you hook a cigarette lighter plug to it*, plug it in, and leave the key in the accessories position you can keep things energized while changing the battery. Then nothing needs to be reset and you can even listen to the sound system while you work. Just be aware that the 12V battery cable will be live and don't let it brush any other metal. Cover it with a rubber glove or something until ready to make the final connection to the new battery.
I used to do this on my Grand Cherokee with a hobby battery though there really was little to actually lose -- radio settings maybe -- while cleaning battery terminals. (I'm not sure if I ever did it on an actual battery changeout for the simple reason that when the old battery was dying attempting to start the car would drop the voltage so low everything was lost anyway and it was moot.)
Never run the engine for this purpose. Besides the mechanical hazard you may destroy auto electronics because with no battery connected the alternator will be delivering wildly pulsating voltage instead of smooth DC. But 12 volts DC from another battery, injected into the lighter socket, will be fine.
If you have every thing prepared you can swap the batteries in 30 sec. The key is in preparation. If you need more time and are capable of not making mistake then you can use jumper cables(as an extension) and pull out the old battery.
Potential problems with the ign key on:
I would err on the side of caution as in some (not not sure about RX) the air bag light may come on.
Problems with chargers as 12v source without battery:
The chargers produce more than 12v to charge the battery (with AC-110 -> transformer -> rectifier as a source the peak voltage can be high). In circuit battery, acts as a clamp and does not allow the voltage to raise higher. So your vehicle electronics may be exposed to over voltage. Having another light current battery is a better solution.
Weighing all the factors, I would opt for a quick swap or let the vehicle loose its memory.
Got the Energizer Max at Walmart for C$87 plus $10 deposit for the old battery. Three-year replacement plus free 3-yr roadside assistance if battery dies.
I like this Energizer since it is not sealed so I can keep an eye on the electrolyte. Current Toyota battery is non-serviceable/sealed.
I never replaced the serviceable battery on the 1998 Sienna that I had for nine years.
Edit: I just measured the Energizer against the Toyota battery and Energizer 108-35N is about two inches shorter/narrower. Does that matter? Battery label says 800 amps at zero degrees, 640 CCA; mfg on Dec 2010.
Thanks. I didn't find any 24Fs (or group 35 fitment 3) in Costco and Walmart - no Optimas in stock yesterday.
Other alternatives were dealer @ C$160 and Canadian Tire @ C$114. I'll take my chance on this Energizer. At any rate, for now, there are more Walmart branches than Costco or Canadian tire for replacement purposes.
^^ Wouldn't a serviceable battery in FL be better than the "sealed" type like the duralast? I believe the problem with heat and battery is the evaporation of the electrolyte. So if you can top up the battery with distilled water, that should prolong the batt's life, no?
CCA ratings is more important for colder climates, the way I understand it.