My EDC is a whole system based around both CR123A and AAA.
On my person, I carry a P1D-CE plus a Battery Junction coin-cell LED on my key ring. I do not usually carry a spare CR123A on my person, but I do tend to watch the level with a ZTS-Mini and I do tend to use low mode quite a bit.
In my man-purse (currently a Max Neatfreak, soon to be a Last Resort when my B-day rolls around) I've got a capped tube, like a cigar tube, that perfectly fits five CR123A and on my main key carabiner I have a waterproof pill bottle that fits one CR123A plus a cotton ball (also good as firestarter). That can be easily slipped in a pocket if I know my P1D-CE cell is getting down to 40% or less.
Then there is the AAA system. In the manpurse I have a Coast Focusing Lenser, a Coast Dual-Color, and a Princeton Tec Impact-II, and a Mag Soli, all running Eneloops. This gives me a wide choice from ~150 lumens OTF, to ~20 floody lumens, to ~2 lumens, plus red. The Impact-II (4xAAA) is mostly considered a waterproof spares carrier for the other lights. Then there's a 35mm film canister with another set of spare AAA, and these are alkalines. Since all the AAA lights are direct drive, they'll run for many hours at reduced output on a set of slowly dying alky's.
I'll have to do some math some day to figure out how much runtime I am carrying with this flexible system. It's a lot.