What is the typical life if one of those hi-tech batteries used as the TCH's 12 volt battery?
Can I expect an alert or MIL when the battery needs to be replaced?

 

I don't remember seeing anything in the manual and the cars are still too new to have battery failure from being old, so don't expect first hand experience. You will get error message if there is something wrong and the car won't start if the battery is depleted, but that's as far as it goes, I think. What usually happens, as the battery is getting older, it looses it's capacity, more so in the cold weather. The car drains some small amount of power, even when shutdown, so if the battery is new and fully charged, you could leave it parked without starting, for about a month or more without problems. As the time goes on , that time will get shorter. At some point the battery will not have enough capacity to last long enough between restarts. The good news is, you only need about 12v and about 10 amps, something even 10 AAA NIMH batteries could deliver to start the car. I would expect the battery to last between 5-10 years if it's taken good care of. My old Honda Accord has regular battery 7 years old now and it works, despite requiring huge load to crank the engine, TCH should last longer , unless the car sits long time or there is some short keeping the battery in low charge state often. I think Prius owners found at least one company that makes similar batteries to Toyota, for much lower price , it should work for TCH as well, but you have long time before need to worry about that.

 

I have run this type of battery in many aircraft over the years and have no problem getting 7 years average with most running 8-9. the thing that will kill this type of battery is overcharge (either by a charger or cars electrical system). I use a pulse on off maintainer milliamp type plugged in year round on the wet matt type batteries or gel cell. Have not used anything on the Camry yet. Most of your ATV and bikes, waterbikes ect are using this type of battery at this time. I think you will see the old complete wet type phased out soon as they cause so much corrossion and cannot be run upside down like then new ones can.