I have performed a Low-mode run-time test, on an Energizer L92 Ultimate Lithium battery.
This battery tested 1.801 volts (no load), and fresh-dated. Room temperature.
Keep in mind -- these results are only for MY sample. Your mileage may vary.
After 5-and-a-half days (132 hours), output had dropped to 50 % brightness.
After 138 hours, output had dropped to 15 %.
At 140 hours, it suddenly went OUT !
Not as long-lasting as your expectations stated above.
But, of course, still a VERY respectable performance !
I'd be interested to hear what numbers other folks get.
BTW -- at the 50 % brightness level, i judged it Quite Similar to my
ZebraLight H51fw, on its lowest setting (Low-Low).
However, the P0 has a wider beam, and is TOTALLY flood.
Hope this information is helpful.
Edited to add --
I used my Minolta Auto Flashmeter III for this test.
It's now 30 years old ( ! ) and still serves me well !