i bought a 48 pack of (I'm just a tiny bit ashamed) of costco alkalines today. currently doing a runtime test, it's supposed to "last" over 20 hours, but we shall see if that's with or without a "resting" period, and whether it's sustained or just if it's on...
As far as eneloops go, I have some that are 7 years old, maybe 20 cycles through them, and they have a tested capacity of 1700mAh. Most likely counterfeits, I had bought them from Amazon back then. They also only sustain the above test light for around 6.5 hours until substantial dimming (i.e. 30ish lumens down to about 5 lumens), whereas my 2400 mAh Olight NiMH sustain about 11 hours before starting to peter out.