I've been EDCing a light for about three years now.
Initially a 3 button cells Streamlight Nano.
In the year I carried it, I probably used it for no more than ten minutes. It only has a few lumens to begin with ( I think 8) and an eight hour run-time, with most of them being sub-lumen. I carried it on my key chain. Like others already said, being primaries, if I used it I would never know how much capacity I had left. So I always wanted the batteries to be fresh.... just in case! Therefore, the light never got used. If I needed one, I would walk to somewhere I had one and grab a different light.
The next year, I carried a single AAA with duraloops in it. A DQG twisty the smallest AAA on the market and in stainless, and a NW XPG2 emitter. I'd top it off when I thought of it... usually once a week. If I actually used it for any amount of time, I'd top it off later that day. For the most part the battery was always nearly fully charged.
This past year, or so, I have been carrying a CooYoo Quantum, in stainless, gifted to me by a friend on the other side of the pond. It is even smaller than my DQG. It runs on a 10180 LiIon, which charges within the light by way of micro USB. I top it off when I think of it, usually about twice a month. It really only gets used for seconds at a time. I am usually near to other larger lights.
Almost all of my lights have rechargeables in them. I have some give away lights with alkys stored with them, and some 2D cell lights in the car, and 2D cell LED Traffic wands.
I have four 3C cell lights that each have an 18650, and a spacer.