I've noticed elevated temperatures seem to greatly accelerate corrosion
in batteries of every description... like leaving flashlights, or
storing spare batteries in the car and/or in the influence of other heat
sources.

For the record, I live in earthquake country and personal experience
through the years has convinced me that wading through debris in the
dark isn't fun anymore.

I have two Mini Mag's I've declared mission critical, and dedicated to
quake emergency use only. One is between the mattresses at the foot of
the bed (along with a good size white painted crow bar). The other is in
a drawer near the front door. Both can be easily located by feel in the
dark, and are placed so they can't roll or tumble away.

To prevent corrosion 'surprises' I replace the batteries in both every
two years, and have my Google calendar set up to automatically remind
me. Both lights are also dated with PostIt tape as a back up.

Of course I also have several other various lights scattered around for
general use, including a robust little 'Pulsar' LED keychain light with
momentary squeeze switch... perfect for quick peeks, and finding a
'real' light should push ever come to shove. The momentary switch works
extremely well at preventing accidental pocket activations. Had it for 6
or 7 years... replaced the batteries twice IIRC.

What I'd like is battery technology that will (economically) allow
flashlights and the like to be stowed corrosion free, long term in
warm/hot environments... like car interiors.

Erik