For safety and convenience I run single cell lights (my one 2 cell CR123 was bought before I understood the issues possible with 2+ cell lights) For simplicity, safety, convenience and run time I use lithium primaries in all my AAA, AA and CR123 lights. I know I can give up run time for lumens by running lithium ion rechargeables but that isn't something I generally have need of or interest in. I also don't go through so many batteries that cost is a big issue. If I burned up a cell every day or two I'd feel differently about that, I'm sure.
I'm sure there are folks who have deeper experience with rechargeables than I do.