Hm, not sure how safe it is to overdischarge a LI-ion battery, but that is an impressive run time. Would probably be even longer if you gave the battery time to rest occasionally, and then add up the running times in the end.
It has a low voltage cut off.
At 60 days, I am going to pull the battery and measure voltage.
One thing I noticed...the light seems to be putting out the same level of light. I guess I expected it to dim a bit toward the end of my test. I do not have a light meter, so this is all just guesswork.
.4 lumens is a pretty low level, but at night, when my eyes adjust, it is almost too bright in my room.