How long my light works? Depends on how many spare batteries I have with me
For professional reasons I was using rechargable batteries my entire life. Alkalines could not do what was needed. That pushed me into trying my best to have AA/AAA NiMh for everything in the house (remotes for TVs, amps, air conditioners, GPS, cappuchino mixers, weather stations, clocks, toys ....). I will not buy a device (if possible) if the device does not run on AA or AAA batteries. I have close about 20 batteris used in apartment alone, not counting 8 flashlights.
But, it was only until in the last years Eneloops came to be (standard 2000 mAh ones with 2000 charges) that I am perfectly satisfied with them. Charge them and forget about them until needed. Leave in a car for years.
I have 15-20 spares (they actually "belong" in my flashes, but when not working, they are spares and in rotation). Plus, in my trousers, at all time I have a small box with one AA and one AAA Eneloop.
Just recently bought y only 18650 lamp with USB charging inbuilt.
Duracells leaked and burned one very expensive lamp we gifted to my wife's father. He would not listen. Now, he also uses Eneloops for everything.
Batteries are nasty stuff to throw away into garbage. Primaries should never be used. This way, with Eneloops, I expect to change batteries (about 40+ in one apartment) once in maybe 10 years. Before Eneloops, NiMhs lasted me probably about 5 years.