A run time evaluation was performed to quantify the observed really long battery life.
The battery was depleted during normal usage, to fully empty.
The effect of a dead battery is that the previously-selected operation mode is forgotten. Normal off/on operation restores the illumination mode that was previously-selected. But, when the battery is dead, then recharged, then turned on, a different illumination mode is provided.
The lamp has a low-battery flicker that is observed when turning off the lamp when the battery is running low. That flicker was observed during this testing.
The empty battery was fully recharged prior to this run time test, until the slow dim flash during charging changed to the a dim constant on. that indicates fully charged.
My operation mode is one flash per second. The measured run time for this mode is 34 hours.