I've used Imoseyon kernel a few times. On beans build 8 I believe it fared the best, but on my current rom(GalaxyMod rls14.1) it sucked my battery dry. I am currently in Ziggys kernel. Not enough time to give a proper reading. I think it was The Executioner ROM that claimed to give easy 15-20 hrs. I don't recall the kernel.
I'm running LeanKernel 1.6 with CleanROM 5.6. It has been less than 24 hours of running this combination, but I'll let you know how things turn out. This particular charge that I am finishing up right now has lasted 12.5 hours and I still have 20% remaining.
Usage consist of:
19% of the battery was used playing just under two hours of GTAIII
31% of usage was Screen
14% Android System
10% Voice calls
9% Android OS
Everything else was 2%
Tomorrow I'll test without playing games, downloading or install apps, etc.
Running with the original settings.
Still has 20% battery at 1d 13h 12m.
v1.7 came out this morning at around 2 a.m. so I'll try it next.
UPDATE:
Ran v1.7 for a few hours only.
Battery life was not as good and the device was running a bit hot as well.
Benchmark testing fell considerably.
Graphics stuttered a few times during drawing in GTAIII.