Will AA's (or AAA's) go off the shelf first?
Of course, but they'll also be easily found in just about any structure in America (I can't speak for other countries). Play a mental game with yourself: walk around today and in every building you enter, think to yourself, "Where could I find AA's here if I needed them?"
I guarantee there are numerous devices you can scavenge them from: remotes, calculators, cameras, toys, clocks, wireless keyboards/mice, etc. Sitting here in my office building, I can look around in a 20 foot radius and spot at least a dozen sources from which to scavenge at least one AA cell, if not more.
It wouldn't surprise me to find out that the only CR123 cells in this whole building are the ones sitting right here in my desk though.
The right AA light (I.E. one with decent voltage tolerance) is great because it can be fed anything: primaries, rechargeables, alkalines, lithiums, etc.
A well regulated AA LED will also give outstanding runtimes these days. The
Fenix L2DCE, for example, offers 55 hours of runtime on low (9 lumens). That is plenty of light to accomplish most tasks and will seem very bright to dark-adapted eyes. I don't know what cell-type yields that particular runtime (I think you can get longer with lithium primaries like the Energizer L91) but let's assume for a second that's the max. How many hours a day do you really plan to use a light? With that kind of runtime, how many spares do you really need? I could very easily get through
a couple of months with an L2DCE and just a few pairs of L91's which weigh practically nothing.
Or what about one of my other favorite utility lights, the
Zebralight H50? I run mine with an AA Eneloop (NiMH cell) as my bedtime reading light
every night. I use it anywhere between 30-60 minutes per night on low, and with all honesty I cannot recall when I last charged the Eneloop inside of it. It must be months by now.
A field doc took a Zebra H30 on a
two-week trip to South America and even though he used it hours every day,
he never once changed the lithium that he started with.
Even if someone were foolish enough not to stock any extra cells in their BOB kit at all, a light like the L2DCE or the H30 would only require that you scavenge in one or two places before you could feed it for ridiculous amounts of time. And if you have lithiums in the light, you can leave them sitting for 10 years and not worry about picking up a dead or leaking light.
It's a no-brainer for me.